351
|
Lu P, Tuszynski MH. Growth factors and combinatorial therapies for CNS regeneration. Exp Neurol 2007; 209:313-20. [PMID: 17927983 DOI: 10.1016/j.expneurol.2007.08.004] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Accepted: 08/01/2007] [Indexed: 12/11/2022]
Abstract
There has been remarkable progress in the last 20 years in understanding mechanisms that underlie the success of axonal regeneration in the peripheral nervous system, and the failure of axonal regeneration in the central nervous system. Following the identification of these underlying mechanisms, several distinct therapeutic approaches have been tested in in vivo models of spinal cord injury (SCI) to enhance central axonal structural plasticity, including the therapeutic administration of neurotrophic factors. While several tested mechanisms apparently enhance axonal growth, more recent, properly controlled studies indicate that experimental approaches to combine therapies that target distinct neural mechanisms achieve greater axonal growth than therapies applied in isolation. The search for combination therapies that optimize axonal growth after SCI continues.
Collapse
Affiliation(s)
- Paul Lu
- Department of Neurosciences, University of California San Diego, La Jolla, CA 92093-0626, USA
| | | |
Collapse
|
352
|
Seijffers R, Mills CD, Woolf CJ. ATF3 increases the intrinsic growth state of DRG neurons to enhance peripheral nerve regeneration. J Neurosci 2007; 27:7911-20. [PMID: 17652582 PMCID: PMC6672733 DOI: 10.1523/jneurosci.5313-06.2007] [Citation(s) in RCA: 294] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Peripheral axons of dorsal root ganglion (DRG) neurons, but not their central axons in the dorsal columns, regenerate after injury. However, if the neurons are conditioned by a peripheral nerve injury into an actively growing state, the rate of peripheral axonal growth is accelerated and the injured central axons begin to regenerate. The growth-promoting effects of conditioning injuries have two components, increased axonal growth and a reduced response to inhibitory myelin cues. We have examined which transcription factors activated by peripheral axonal injury may mediate the conditioning effect by regulating expression of effectors that increase the intrinsic growth state of the neurons. Activating transcription factor 3 (ATF3) is a prime candidate because it is induced in all injured DRG neurons after peripheral, but not central, axonal damage. To investigate if ATF3 promotes regeneration, we generated transgenic mice that constitutively express this transcription factor in non-injured adult DRG neurons. The rate of peripheral nerve regeneration was enhanced in the transgenic mice to an extent comparable to that produced by a preconditioning nerve injury. The expression of some growth-associated genes, such as SPRR1A, but not others like GAP-43, was increased in the non-injured neurons. ATF3 increased DRG neurite elongation when cultured on permissive substrates but did not overcome the inhibitory effects of myelin or promote central axonal regeneration in the spinal cord in vivo. We conclude that ATF3 contributes to nerve regeneration by increasing the intrinsic growth state of injured neurons.
Collapse
Affiliation(s)
- Rhona Seijffers
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| | - Charles D. Mills
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| | - Clifford J. Woolf
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| |
Collapse
|
353
|
Mills CD, Allchorne AJ, Griffin RS, Woolf CJ, Costigan M. GDNF selectively promotes regeneration of injury-primed sensory neurons in the lesioned spinal cord. Mol Cell Neurosci 2007; 36:185-94. [PMID: 17702601 PMCID: PMC2034440 DOI: 10.1016/j.mcn.2007.06.011] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2007] [Revised: 06/15/2007] [Accepted: 06/20/2007] [Indexed: 11/26/2022] Open
Abstract
Axonal regeneration within the CNS fails due to the growth inhibitory environment and the limited intrinsic growth capacity of injured neurons. Injury to DRG peripheral axons induces expression of growth associated genes including members of the glial-derived neurotrophic factor (GDNF) signaling pathway and "preconditions" the injured cells into an active growth state, enhancing growth of their centrally projecting axons. Here, we show that preconditioning DRG neurons prior to culturing increased neurite outgrowth, which was further enhanced by GDNF in a bell-shaped growth response curve. In vivo, GDNF delivered directly to DRG cell bodies facilitated the preconditioning effect, further enhancing axonal regeneration beyond spinal cord lesions. Consistent with the in vitro results, the in vivo effect was seen only at low GDNF concentrations. We conclude that peripheral nerve injury upregulates GDNF signaling pathway components and that exogenous GDNF treatment selectively promotes axonal growth of injury-primed sensory neurons in a concentration-dependent fashion.
Collapse
Affiliation(s)
- Charles D Mills
- Neural Plasticity Research Group, Massachusetts General Hospital and Harvard Medical School, 149 13th Street, Charlestown, MA 02129, USA
| | | | | | | | | |
Collapse
|
354
|
Gross RE, Mei Q, Gutekunst CA, Torre E. The pivotal role of RhoA GTPase in the molecular signaling of axon growth inhibition after CNS injury and targeted therapeutic strategies. Cell Transplant 2007; 16:245-62. [PMID: 17503736 DOI: 10.3727/000000007783464740] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The dogma that the adult central nervous system (CNS) is nonpermissive to axonal regeneration is beginning to fall in the face of increased understanding of the molecular and cellular biology of axon outgrowth. It is now appreciated that axon growth is regulated by a combination of extracellular factors related to the milieu of the developing or adult CNS and the presence of injury, and intracellular factors related to the "growth state" of the developing or regenerating neuron. Several critical points of convergence within the developing or regenerating neuron for mediating intracellular cell signaling effects on the growth cone cytoskeleton have been identified, and their modulation has produced marked increases in axon outgrowth within the "nonpermissive" milieu of the adult injured CNS. One such critical convergence point is the small GTPase RhoA, which integrates signaling events produced by both myelin-associated inhibitors (e.g., NogoA) and astroglial-derived inhibitors (chondroitin sulfate proteoglycans) and regulates the activity of downstream effectors that modulate cytoskeletal dynamics within the growth cone mediating axon outgrowth or retraction. Inhibition of RhoA has been associated with increased outgrowth on nonpermissive substrates in vitro and increased axon regeneration in vivo. We are developing lentiviral vectors that modulate RhoA activity, allowing more long-term expression than is possible with current approaches. These vectors may be useful in regenerative strategies for spinal cord injury, brain injury, and neurodegenerative diseases including Parkinson's disease, Alzheimer's disease, and Huntington's disease.
Collapse
Affiliation(s)
- Robert E Gross
- Department of Neurosurgery, Center for Neurodegenerative Diseases, Emory University School of Medicine, Atlanta, GA 30322, USA.
| | | | | | | |
Collapse
|
355
|
Gardiner NJ, Moffatt S, Fernyhough P, Humphries MJ, Streuli CH, Tomlinson DR. Preconditioning injury-induced neurite outgrowth of adult rat sensory neurons on fibronectin is mediated by mobilisation of axonal α5 integrin. Mol Cell Neurosci 2007; 35:249-60. [PMID: 17433878 DOI: 10.1016/j.mcn.2007.02.020] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2006] [Revised: 02/21/2007] [Accepted: 02/26/2007] [Indexed: 10/23/2022] Open
Abstract
A preconditioning sciatic nerve crush promotes the capacity of adult sensory neurons to regenerate following a subsequent injury to their axons. The increase in regeneration is detected in cultures of dissociated neurons, as an earlier and enhanced rate of neurite elongation. We compare neurotrophin-stimulated neurite outgrowth from sensory neurons on laminin and fibronectin. There is a poor response of sensory neurons to fibronectin in comparison to laminin, but this is enhanced by a preconditioning lesion to the sciatic nerve 7 days prior to culture. By using specific integrin-binding fibronectin fragments and function-blocking antibodies, we demonstrate that the enhanced preconditioned neurite outgrowth on fibronectin is largely mediated by alpha5beta1 integrin. Preconditioning injury alter the subcellular localisation of alpha5 integrin in preconditioned neurites. We show that alpha5 integrin localises to adhesion complexes in the growth cone and neurites of preconditioned neurons, but not control neurons.
Collapse
Affiliation(s)
- Natalie J Gardiner
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.
| | | | | | | | | | | |
Collapse
|
356
|
Abstract
Numerous studies in the last two decades have resulted in significant progress in our understanding of the role of inhibitors on axonal regeneration and conditions that influence mature neurons to regrow in an inhibitory environment. These studies have revealed putative therapeutic targets and strategies to interfere in the inhibitory signaling cascade and promote axonal regeneration. Some agents that were successful in animal models are now being tested in human patients. All of these advances have raised hope of a cure for an injury that was once thought to be 'an ailment for which nothing is done' (Quote from Edwin Smith surgical papyrus, 1600BC).
Collapse
|
357
|
Tan AM, Petruska JC, Mendell LM, Levine JM. Sensory afferents regenerated into dorsal columns after spinal cord injury remain in a chronic pathophysiological state. Exp Neurol 2007; 206:257-68. [PMID: 17585905 PMCID: PMC3103885 DOI: 10.1016/j.expneurol.2007.05.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Revised: 05/02/2007] [Accepted: 05/04/2007] [Indexed: 10/23/2022]
Abstract
Axon regeneration after experimental spinal cord injury (SCI) can be promoted by combinatorial treatments that increase the intrinsic growth capacity of the damaged neurons and reduce environmental factors that inhibit axon growth. A prior peripheral nerve conditioning lesion is a well-established means of increasing the intrinsic growth state of sensory neurons whose axons project within the dorsal columns of the spinal cord. Combining such a prior peripheral nerve conditioning lesion with the infusion of antibodies that neutralize the growth inhibitory effects of the NG2 chondroitin sulfate proteoglycan promotes sensory axon growth through the glial scar and into the white matter of the dorsal columns. The physiological properties of these regenerated axons, particularly in the chronic SCI phase, have not been established. Here we examined the functional status of regenerated sensory afferents in the dorsal columns after SCI. Six months post-injury, we located and electrically mapped functional sensory axons that had regenerated beyond the injury site. The regenerated axons had reduced conduction velocity, decreased frequency-following ability, and increasing latency to repetitive stimuli. Many of the axons that had regenerated into the dorsal columns rostral to the injury site were chronically demyelinated. These results demonstrate that regenerated sensory axons remain in a chronic pathophysiological state and emphasize the need to restore normal conduction properties to regenerated axons after spinal cord injury.
Collapse
Affiliation(s)
- Andrew M Tan
- Department of Neurobiology and Behavior, SUNY at Stony Brook, Stony Brook, NY 11794, USA
| | | | | | | |
Collapse
|
358
|
Pasterkamp RJ, Verhaagen J. Semaphorins in axon regeneration: developmental guidance molecules gone wrong? Philos Trans R Soc Lond B Biol Sci 2007; 361:1499-511. [PMID: 16939971 PMCID: PMC1664670 DOI: 10.1098/rstb.2006.1892] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Semaphorins are developmental axon guidance cues that continue to be expressed during adulthood and are regulated by neural injury. During the formation of the nervous system, repulsive semaphorins guide axons to their targets by restricting and channelling their growth. They affect the growth cone cytoskeleton through interactions with receptor complexes that are linked to a complicated intracellular signal transduction network. Following injury, regenerating axons stop growing when they reach the border of the glial-fibrotic scar, in part because they encounter a potent molecular barrier that inhibits growth cone extension. A number of secreted semaphorins are expressed in the glial-fibrotic scar and at least one transmembrane semaphorin is upregulated in oligodendrocytes surrounding the lesion site. Semaphorin receptors, and many of the signal transduction components required for semaphorin signalling, are present in injured central nervous system neurons. Here, we review evidence that supports a critical role for semaphorin signalling in axon regeneration, and highlight a number of challenges that lie ahead with respect to advancing our understanding of semaphorin function in the normal and injured adult nervous system.
Collapse
Affiliation(s)
- R. Jeroen Pasterkamp
- Department of Pharmacology and Anatomy, Rudolf Magnus Institute of NeuroscienceUniversity Medical Center Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
- Authors for correspondence () ()
| | - Joost Verhaagen
- Netherlands Institute for NeuroscienceMeibergdreef 33, 1105 AZ, Amsterdam, The Netherlands
- Authors for correspondence () ()
| |
Collapse
|
359
|
Romero MI, Lin L, Lush ME, Lei L, Parada LF, Zhu Y. Deletion of Nf1 in neurons induces increased axon collateral branching after dorsal root injury. J Neurosci 2007; 27:2124-34. [PMID: 17314307 PMCID: PMC6673560 DOI: 10.1523/jneurosci.4363-06.2007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Ras-mediated signaling pathways participate in multiple aspects of neural development and function. For example, Ras signaling lies downstream of neurotrophic factors and Trk family receptor tyrosine kinases to regulate neuronal survival and morphological differentiation, including axon extension and target innervation. Neurofibromin, the protein encoded by the tumor suppressor gene Nf1, is a negative regulator of Ras [Ras-GAP (GTPase-activating protein)], and we previously demonstrated that Nf1 null embryonic sensory and sympathetic neurons can survive and differentiate independent of neurotrophin support. In this report, we demonstrate that Nf1 loss in adult sensory neurons enhances their intrinsic capacity for neurite outgrowth and collateral branching in vitro and in vivo after dorsal root injury. In contrast to the permanent sensory deficits observed in control mice after dorsal rhizotomy, neuron-specific Nf1 mutant mice spontaneously recover proprioceptive function. This phenomenon appears to be mediated both by a cell-autonomous capacity of spared Nf1-/- DRG neurons for increased axonal sprouting, and by non-cell-autonomous contribution from Nf1-/- neurons in the denervated spinal cord.
Collapse
Affiliation(s)
- Mario I. Romero
- Department of Developmental Biology and Kent Waldrep Foundation Center for Basic Neuroscience Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9133
| | - Lu Lin
- Department of Developmental Biology and Kent Waldrep Foundation Center for Basic Neuroscience Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9133
| | - Mark E. Lush
- Department of Developmental Biology and Kent Waldrep Foundation Center for Basic Neuroscience Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9133
| | - Lei Lei
- Department of Developmental Biology and Kent Waldrep Foundation Center for Basic Neuroscience Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9133
| | - Luis F. Parada
- Department of Developmental Biology and Kent Waldrep Foundation Center for Basic Neuroscience Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9133
| | - Yuan Zhu
- Department of Developmental Biology and Kent Waldrep Foundation Center for Basic Neuroscience Research on Nerve Growth and Regeneration, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9133
| |
Collapse
|
360
|
Zurn AD, Bandtlow CE. Regeneration failure in the CNs: cellular and molecular mechanisms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 557:54-76. [PMID: 16955704 DOI: 10.1007/0-387-30128-3_4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Anne D Zurn
- Department of Experimental Surgery, Lausanne University Hospital, Faculty of Biology and Medicine, Switzerland
| | | |
Collapse
|
361
|
Kim WY, Zhou FQ, Zhou J, Yokota Y, Wang YM, Yoshimura T, Kaibuchi K, Woodgett JR, Anton E, Snider WD. Essential roles for GSK-3s and GSK-3-primed substrates in neurotrophin-induced and hippocampal axon growth. Neuron 2007; 52:981-96. [PMID: 17178402 PMCID: PMC4167845 DOI: 10.1016/j.neuron.2006.10.031] [Citation(s) in RCA: 174] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Revised: 09/19/2006] [Accepted: 10/27/2006] [Indexed: 01/23/2023]
Abstract
Glycogen synthase kinase-3beta (GSK-3beta) is thought to mediate morphological responses to a variety of extracellular signals. Surprisingly, we found no gross morphological deficits in nervous system development in GSK-3beta null mice. We therefore designed an shRNA that targeted both GSK-3 isoforms. Strong knockdown of both GSK-3alpha and beta markedly reduced axon growth in dissociated cultures and slice preparations. We then assessed the role of different GSK-3 substrates in regulating axon morphology. Elimination of activity toward primed substrates only using the GSK-3 R96A mutant was associated with a defect in axon polarity (axon branching) compared to an overall reduction in axon growth induced by a kinase-dead mutant. Consistent with this finding, moderate reduction of GSK-3 activity by pharmacological inhibitors induced axon branching and was associated primarily with effects on primed substrates. Our results suggest that GSK-3 is a downstream convergent point for many axon growth regulatory pathways and that differential regulation of primed versus all GSK-3 substrates is associated with a specific morphological outcome.
Collapse
MESH Headings
- Animals
- Axons/drug effects
- Axons/physiology
- Blotting, Western
- Cell Count/methods
- Cells, Cultured
- Dose-Response Relationship, Drug
- Drug Interactions
- Embryo, Mammalian
- Fluorescent Antibody Technique/methods
- Ganglia, Spinal/cytology
- Ganglia, Spinal/drug effects
- Gene Expression Regulation, Developmental/drug effects
- Gene Expression Regulation, Developmental/physiology
- Glycogen Synthase Kinase 3/antagonists & inhibitors
- Glycogen Synthase Kinase 3/physiology
- Hippocampus/cytology
- In Vitro Techniques
- Indoles/pharmacology
- Mice
- Mice, Knockout
- Microtubule-Associated Proteins/physiology
- Models, Biological
- Mutation/physiology
- Neocortex/cytology
- Neocortex/drug effects
- Nerve Growth Factor/pharmacology
- Neurons/cytology
- Neurons/drug effects
- Oximes/pharmacology
- Transfection/methods
Collapse
Affiliation(s)
- Woo-Yang Kim
- UNC Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Feng-Quan Zhou
- UNC Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
- Departments of Orthopedic Surgery and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287
| | - Jiang Zhou
- UNC Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Yukako Yokota
- UNC Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
- Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Yan-Min Wang
- UNC Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Takeshi Yoshimura
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa-ku, Nagoya, Aichi 466-8550, Japan
| | - Kozo Kaibuchi
- Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa-ku, Nagoya, Aichi 466-8550, Japan
| | - James R. Woodgett
- Ontario Cancer Institute, 610 University Avenue, Toronto, Ontario M5G 2M9, Canada
| | - Eva Anton
- UNC Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
- Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - William D. Snider
- UNC Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
- Corresponding author and complete address: William D. Snider, Neuroscience Center, University of North Carolina at Chapel Hill, 8129 Neuroscience Research Building, 105 Mason Farm, Chapel Hill, NC 27599,
| |
Collapse
|
362
|
Hannila SS, Siddiq MM, Filbin MT. Therapeutic Approaches to Promoting Axonal Regeneration in the Adult Mammalian Spinal Cord. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2007; 77:57-105. [PMID: 17178472 DOI: 10.1016/s0074-7742(06)77003-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Sari S Hannila
- Department of Biological Sciences, Hunter College, City University of New York, New York 10021, USA
| | | | | |
Collapse
|
363
|
Cai J, Ziemba KS, Smith GM, Jin Y. Evaluation of cellular organization and axonal regeneration through linear PLA foam implants in acute and chronic spinal cord injury. J Biomed Mater Res A 2007; 83:512-20. [PMID: 17503492 DOI: 10.1002/jbm.a.31296] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
There are few studies of neural implants in spinal cord injury (SCI) focused on supporting directed axon growth. In this study, we fabricated a macroporous poly (lactic acid) (PLA) foam with oriented inner channels. Amorphous foam without linear channels served as a control in an acute SCI injury model, and the effectiveness of foam with linear channels was further investigated in a chronic SCI model. Implants were placed into a 2 mm hemisection lesion cavity at the T8 spinal cord level in adult rats. Two weeks post-implantation, tissue sections including the implants were examined using antibodies against GFAP, p75, ED-1, laminin, GAP-43, and CGRP. Foam implants were well-integrated with the host spinal cord. In linear foams, numerous DAPI-stained cells were found within the inner channels. Schwann cells but not astrocytes had migrated within the channels. Intense laminin staining was observed throughout the extracellular matrix substrate. GAP-43- and CGRP-positive axons grew through the implants following the linear channels. In the amorphous control foams, DAPI staining distributed evenly through the pores. However, the growth of GAP-43 or CGRP-positive axons was misguided and impeded at the entrance area of the foam. Higher numbers of GAP-43 and CGRP-positive axons grew into linear foam implants after chronic SCI than acute SCI. These results suggest the potential application of linear foam implants in cell and axon guidance for SCI repair, especially for chronic SCI.
Collapse
Affiliation(s)
- Jie Cai
- Department of Physiology, University of Kentucky, Lexington, Kentucky 40536-0298, USA
| | | | | | | |
Collapse
|
364
|
de Wit J, Verhaagen J. Proteoglycans as modulators of axon guidance cue function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 600:73-89. [PMID: 17607948 DOI: 10.1007/978-0-387-70956-7_7] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Organizing a functional neuronal network requires the precise wiring of neuronal connections. In order to find their correct targets, growth cones navigate through the extracellular matrix guided by secreted and membrane-bound molecules of the slit, netrin, ephrin and semaphorin families. Although many of these axon guidance molecules are able to bind to heparan sulfate proteoglycans, the role of proteoglycans in regulating axon guidance cue function is only now beginning to be understood. Recent developmental studies in a wide range of model organisms have revealed a crucial role for heparan sulfate proteoglycans as modulators of key signaling pathways in axon guidance. In addition, emerging evidence indicates an essential role for chondroitin sulfate proteoglycans in modifying the guidance function of semaphorins. It is becoming increasingly clear that extracellular matrix molecules, rather than just constituting a structural scaffold, can critically influence axon guidance cue function in development, and may continue to do so in the injured adult nervous system.
Collapse
Affiliation(s)
- Joris de Wit
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands.
| | | |
Collapse
|
365
|
Rossi F, Gianola S, Corvetti L. Regulation of intrinsic neuronal properties for axon growth and regeneration. Prog Neurobiol 2006; 81:1-28. [PMID: 17234322 DOI: 10.1016/j.pneurobio.2006.12.001] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Revised: 11/04/2006] [Accepted: 12/05/2006] [Indexed: 01/29/2023]
Abstract
Regulation of neuritic growth is crucial for neural development, adaptation and repair. The intrinsic growth potential of nerve cells is determined by the activity of specific molecular sets, which sense environmental signals and sustain structural extension of neurites. The expression and function of these molecules are dynamically regulated by multiple mechanisms, which adjust the actual growth properties of each neuron population at different ontogenetic stages or in specific conditions. The neuronal potential for axon elongation and regeneration are restricted at the end of development by the concurrent action of several factors associated with the final maturation of neurons and of the surrounding tissue. In the adult, neuronal growth properties can be significantly modulated by injury, but they are also continuously tuned in everyday life to sustain physiological plasticity. Strict regulation of structural remodelling and neuritic elongation is thought to be required to maintain specific patterns of connectivity in the highly complex mammalian CNS. Accordingly, procedures that neutralize such mechanisms effectively boost axon growth in both intact and injured nervous system. Even in these conditions, however, aberrant connections are only formed in the presence of unusual external stimuli or experience. Therefore, growth regulatory mechanisms play an essentially permissive role by setting the responsiveness of neural circuits to environmental stimuli. The latter exert an instructive action and determine the actual shape of newly formed connections. In the light of this notion, efficient therapeutic interventions in the injured CNS should combine targeted manipulations of growth control mechanisms with task-specific training and rehabilitation paradigms.
Collapse
Affiliation(s)
- Ferdinando Rossi
- Rita Levi Montalcini Centre for Brain Repair, Department of Neuroscience, University of Turin, Corso Raffaello 30, I-10125 Turin, Italy.
| | | | | |
Collapse
|
366
|
Shoemaker SE, Sachs HH, Vaccariello SA, Zigmond RE. Reduction in nerve growth factor availability leads to a conditioning lesion-like effect in sympathetic neurons. ACTA ACUST UNITED AC 2006; 66:1322-37. [PMID: 16967509 DOI: 10.1002/neu.20297] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Axotomized peripheral neurons are capable of regeneration, and the rate of regeneration can be enhanced by a conditioning lesion (i.e., a lesion prior to the lesion after which neurite outgrowth is measured). A possible signal that could trigger the conditioning lesion effect is the reduction in availability of a target-derived factor resulting from the disconnection of a neuron from its target tissue. We tested this hypothesis with respect to nerve growth factor (NGF) and sympathetic neurons by administering an antiserum to NGF to adult mice for 7 days prior to explantation or dissociation of the superior cervical ganglion (SCG) and subsequently measuring neurite outgrowth. The antiserum treatment dramatically lowered the concentration of NGF in the SCG and increased the rate of neurite outgrowth in both explants and cell cultures. The increase in neurite outgrowth was similar in magnitude to that seen after a conditioning lesion. To determine if exogenous NGF could block the effect of a conditioning lesion, mice were injected with NGF or cytochrome C immediately prior to unilateral axotomy of the SCG, and for 7 days thereafter. A conditioning lesion effect of similar magnitude was seen in NGF-treated and control animals. While NGF treatment increased NGF levels in the contralateral control ganglion, it did not significantly elevate levels in the axotomized ganglion. The results suggest that the decreased availability of NGF after axotomy is a sufficient stimulus to induce the conditioning lesion effect in sympathetic neurons. While NGF administration did not prevent the conditioning lesion effect, this may be due to the markedly decreased ability of sympathetic neurons to accumulate the growth factor after axotomy.
Collapse
Affiliation(s)
- S E Shoemaker
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4975, USA
| | | | | | | |
Collapse
|
367
|
Wu D, Zhang Y, Bo X, Huang W, Xiao F, Zhang X, Miao T, Magoulas C, Subang MC, Richardson PM. Actions of neuropoietic cytokines and cyclic AMP in regenerative conditioning of rat primary sensory neurons. Exp Neurol 2006; 204:66-76. [PMID: 17112514 DOI: 10.1016/j.expneurol.2006.09.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Revised: 09/26/2006] [Accepted: 09/29/2006] [Indexed: 12/16/2022]
Abstract
A conditioning lesion to peripheral axons of primary sensory neurons accelerates regeneration of their central axons in vivo or neurite outgrowth if the neurons are grown in vitro. Previous evidence has implicated neuropoietic cytokines and also cyclic AMP in regenerative conditioning. In experiments reported here, delivery through a lentivirus vector of ciliary neurotrophic factor to the appropriate dorsal root ganglion in rats was sufficient to mimic the conditioning effect of peripheral nerve injury on the regeneration of dorsal spinal nerve root axons. Regeneration in this experimental preparation was also stimulated by intraganglionic injection of dibutyryl cyclic AMP but the effects of ciliary neurotrophic factor and dibutyryl cyclic AMP were not additive. Dibutyryl cyclic AMP injection into the dorsal root ganglion induced mRNAs for two other neuropoietic cytokines, interleukin-6 and leukemia inhibitory factor and increased the accumulation of phosphorylated STAT3 in neuronal nuclei. The in vitro conditioning action of dibutyryl cyclic AMP was partially blocked by a pharmacological inhibitor of Janus kinase 2, a neuropoietic cytokine signaling molecule. We suggest that the beneficial actions of increased cyclic AMP activity on axonal regeneration of primary sensory neurons are mediated, at least in part, through the induction of neuropoietic cytokine synthesis within the dorsal root ganglion.
Collapse
Affiliation(s)
- Dongsheng Wu
- Center for Neuroscience, Institute of Cell and Molecular Sciences, Barts and The London, Queen Mary's School of Medicine, University of London, 4 Newark Street, London E1 2AT, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
368
|
Barritt AW, Davies M, Marchand F, Hartley R, Grist J, Yip P, McMahon SB, Bradbury EJ. Chondroitinase ABC promotes sprouting of intact and injured spinal systems after spinal cord injury. J Neurosci 2006; 26:10856-67. [PMID: 17050723 PMCID: PMC3339436 DOI: 10.1523/jneurosci.2980-06.2006] [Citation(s) in RCA: 331] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Chondroitin sulfate proteoglycans (CSPGs) are inhibitory extracellular matrix molecules that are upregulated after CNS injury. Degradation of CSPGs using the enzyme chondroitinase ABC (ChABC) can promote functional recovery after spinal cord injury. However, the mechanisms underlying this recovery are not clear. Here we investigated the effects of ChABC treatment on promoting plasticity within the spinal cord. We found robust sprouting of both injured (corticospinal) and intact (serotonergic) descending projections as well as uninjured primary afferents after a cervical dorsal column injury and ChABC treatment. Sprouting fibers were observed in aberrant locations in degenerating white matter proximal to the injury in regions where CSPGs had been degraded. Corticospinal and serotonergic sprouting fibers were also observed in spinal gray matter at and below the level of the lesion, indicating increased innervation in the terminal regions of descending projections important for locomotion. Spinal-injured animals treated with a vehicle solution showed no significant sprouting. Interestingly, ChABC treatment in uninjured animals did not induce sprouting in any system. Thus, both denervation and CSPG degradation were required to promote sprouting within the spinal cord. We also examined potential detrimental effects of ChABC-induced plasticity. However, although primary afferent sprouting was observed after lumbar dorsal column lesions and ChABC treatment, there was no increased connectivity of nociceptive neurons or development of mechanical allodynia or thermal hyperalgesia. Thus, CSPG digestion promotes robust sprouting of spinal projections in degenerating and denervated areas of the spinal cord; compensatory sprouting of descending systems could be a key mechanism underlying functional recovery.
Collapse
Affiliation(s)
- A W Barritt
- Neurorestoration Group, Wolfson Centre for Age Related Diseases, King's College London, London SE1 1UL, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
369
|
Miao T, Wu D, Zhang Y, Bo X, Subang MC, Wang P, Richardson PM. Suppressor of cytokine signaling-3 suppresses the ability of activated signal transducer and activator of transcription-3 to stimulate neurite growth in rat primary sensory neurons. J Neurosci 2006; 26:9512-9. [PMID: 16971535 PMCID: PMC6674589 DOI: 10.1523/jneurosci.2160-06.2006] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The actions of the neuropoietic cytokines are mediated by the gp130 receptor, which activates several signaling molecules including the transcription factor STAT3 (signal transducer and activator of transcription), which, in turn, is subject to feedback inhibition by SOCS3 (suppressor of cytokine signaling). Activation of the gp130 receptor has been implicated in axonal growth particularly during regeneration, but the specific contribution of STAT3 is the subject of conflicting reports. Measurements of SOCS3 mRNA in rat dorsal root ganglia showed a significant induction in this inhibitory molecule after peripheral nerve injury. The functions of STAT3 and SOCS3 in adult rat primary sensory neurons were investigated in vitro through transduction of lentiviruses yielding a conditionally activated STAT3, native SOCS3, or a mutant SOCS3 with dominant-negative actions. The SOCS3 construct was effective in inhibiting tyrosine phosphorylation of STAT3 in a neuroblastoma cell line and in blocking nuclear accumulation of endogenous STAT3 or of the conditionally activated STAT3 chimera in primary sensory neurons. In such neurons, transduction and activation of STAT3 enhanced neurite growth, transduction with SOCS3 reduced neurite outgrowth, and transduction with mutant SOCS3 enhanced neurite growth, at least under basal conditions. In conclusion, STAT3 signaling is beneficial to axonal growth through activating transcription of unidentified genes, and SOCS3 is detrimental to axonal growth through inhibition of STAT3 and/or other transcription factors.
Collapse
MESH Headings
- Active Transport, Cell Nucleus/physiology
- Animals
- Axotomy
- Cell Differentiation/physiology
- Cell Line, Tumor
- Cells, Cultured
- Feedback, Physiological/physiology
- Ganglia, Spinal/cytology
- Ganglia, Spinal/embryology
- Ganglia, Spinal/metabolism
- Gene Expression Regulation, Developmental/physiology
- Genetic Vectors/genetics
- Humans
- Mice
- Nerve Regeneration/genetics
- Neurites/metabolism
- Neurites/ultrastructure
- Neurons, Afferent/cytology
- Neurons, Afferent/metabolism
- RNA, Messenger/metabolism
- Rats
- STAT3 Transcription Factor/genetics
- STAT3 Transcription Factor/physiology
- Sciatic Neuropathy/genetics
- Sciatic Neuropathy/metabolism
- Sciatic Neuropathy/physiopathology
- Signal Transduction/physiology
- Suppressor of Cytokine Signaling 3 Protein
- Suppressor of Cytokine Signaling Proteins/genetics
- Suppressor of Cytokine Signaling Proteins/physiology
- Transfection
Collapse
Affiliation(s)
| | | | | | | | | | - Ping Wang
- Gastroenterology, Barts and the London Queen Mary's School of Medicine, University of London, London E1 2AT, United Kingdom
| | | |
Collapse
|
370
|
Höke A. Mechanisms of Disease: what factors limit the success of peripheral nerve regeneration in humans? ACTA ACUST UNITED AC 2006; 2:448-54. [PMID: 16932603 DOI: 10.1038/ncpneuro0262] [Citation(s) in RCA: 229] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2006] [Accepted: 06/07/2006] [Indexed: 02/05/2023]
Abstract
Functional recovery after repair of peripheral nerve injury in humans is often suboptimal. Over the past quarter of a century, there have been significant advances in human nerve repair, but most of the developments have been in the optimization of surgical techniques. Despite extensive research, there are no current therapies directed at the molecular mechanisms of nerve regeneration. Multiple interventions have been shown to improve nerve regeneration in small animal models, but have not yet translated into clinical therapies for human nerve injuries. In many rodent models, regeneration occurs over relatively short distances, so the duration of denervation is short. By contrast, in humans, nerves often have to regrow over long distances, and the distal portion of the nerve progressively loses its ability to support regeneration during this process. This can be largely attributed to atrophy of Schwann cells and loss of a Schwann cell basal lamina tube, which results in an extracellular environment that is inhibitory to nerve regeneration. To develop successful molecular therapies for nerve regeneration, we need to generate animal models that can be used to address the following issues: improving the intrinsic ability of neurons to regenerate to increase the speed of axonal outgrowth; preventing loss of basal lamina and chronic denervation changes in the denervated Schwann cells; and overcoming inhibitory cues in the extracellular matrix.
Collapse
Affiliation(s)
- Ahmet Höke
- Neuromuscular Division, Department of Neurology at Johns Hopkins Hospital, Baltimore, MD 21287, USA.
| |
Collapse
|
371
|
Harel NY, Strittmatter SM. Can regenerating axons recapitulate developmental guidance during recovery from spinal cord injury? Nat Rev Neurosci 2006; 7:603-16. [PMID: 16858389 PMCID: PMC2288666 DOI: 10.1038/nrn1957] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The precise wiring of the adult mammalian CNS originates during a period of stunning growth, guidance and plasticity that occurs during and shortly after development. When injured in adults, this intricate system fails to regenerate. Even when the obstacles to regeneration are cleared, growing adult CNS fibres usually remain misdirected and fail to reform functional connections. Here, we attempt to fill an important niche related to the topics of nervous system development and regeneration. We specifically contrast the difficulties faced by growing fibres within the adult context to the precise circuit-forming capabilities of developing fibres. In addition to focusing on methods to stimulate growth in the adult, we also expand on approaches to recapitulate development itself.
Collapse
Affiliation(s)
- Noam Y Harel
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
| | | |
Collapse
|
372
|
Abstract
Damage to the adult CNS often leads to persistent deficits due to the inability of mature axons to regenerate after injury. Mounting evidence suggests that the glial environment of the adult CNS, which includes inhibitory molecules in CNS myelin as well as proteoglycans associated with astroglial scarring, might present a major hurdle for successful axon regeneration. Here, we evaluate the molecular basis of these inhibitory influences and their contributions to the limitation of long-distance axon repair and other types of structural plasticity. Greater insight into glial inhibition is crucial for developing therapies to promote functional recovery after neural injury.
Collapse
Affiliation(s)
- Glenn Yiu
- Division of Neuroscience, Children's Hospital, Boston, Massachusetts 02115, USA
| | | |
Collapse
|
373
|
|
374
|
Abstract
There are now numerous preclinical reports of various experimental treatments promoting some functional recovery after spinal cord injury. Surprisingly, perhaps, the mechanisms that underlie recovery have rarely been definitively established. Here, we critically evaluate the evidence that regeneration of damaged pathways or compensatory collateral sprouting can promote recovery. We also discuss several more speculative mechanisms that might putatively explain or confound some of the reported outcomes of experimental interventions.
Collapse
Affiliation(s)
- Elizabeth J Bradbury
- Neurorestoration Group, Wolfson Wing, Hodgkin Building, Guy's Campus, King's College London, London Bridge, London SE1 1UL, UK
| | | |
Collapse
|
375
|
Challa M, Chapa GR, Govindaraju S, González-García M, Ballestero RP. Characterization of the domains of zRICH, a protein induced during optic nerve regeneration in zebrafish. Brain Res 2006; 1100:42-54. [PMID: 16765331 DOI: 10.1016/j.brainres.2006.04.123] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Revised: 04/26/2006] [Accepted: 04/30/2006] [Indexed: 01/03/2023]
Abstract
Teleost fish show a remarkable capability of nerve regeneration in their CNS, while injuries to axon fibers in the CNS of mammals result in degeneration and loss of function. Understanding this difference has biomedical consequences to humans. Both extrinsic factors from the neuronal environment and intrinsic neuronal factors seem to play a role in successful nerve regeneration. Among the intrinsic factors, a number of proteins termed axonal growth associated proteins (GAPs) are strongly induced during axon regeneration. RICH proteins are axonal GAPs that show homology to mammalian myelin marker proteins termed CNPases. Sequence analysis distinguishes three domains in these proteins. In this report, mutant versions of zebrafish RICH proteins were generated to study the roles of the domains of the protein at biochemical and cellular levels. The central CNPase homology domain was sufficient for catalytic activity. The amino terminal acidic domain causes the anomalous electrophoretic migration observed for RICH proteins. The small C-terminal domain bears an isoprenylation motif and is necessary for the interaction of zRICH with cellular membranes. At the cellular level, expression of wild-type zRICH protein in PC12 cells did not induce neurite generation. Additionally, neither the expression of wild-type zRICH nor the expression of mutant versions of the protein interfered with the levels of differentiation of PC12 cells induced by nerve growth factor, suggesting that, at least in this model of neuronal differentiation, zRICH proteins do not participate in the process of generation of neurites.
Collapse
Affiliation(s)
- Madhavi Challa
- Department of Chemistry, Texas A&M University-Kingsville, 700 University Boulevard, Kingsville, TX, USA
| | | | | | | | | |
Collapse
|
376
|
Abstract
Inhibition by several inhibitory molecules on oligodendrocytes, and by chondroitin sulphate proteoglycans and semaphorins in the glial scar discourages regeneration of axons in the injured spinal cord. This inhibition is compounded by the poor regenerative ability of most central nervous system (CNS) axons. Treatments that block some of these inhibitory mechanisms promote regeneration in animal models of cord injury. Plasticity is also reduced by some of the inhibitory molecules, and some of the treatments that promote regeneration also promote plasticity. This is probably a more achievable therapeutic target than axon regeneration, and an effective treatment would be of assistance to the majority of patients with partial cord injuries.
Collapse
Affiliation(s)
- James W Fawcett
- Cambridge University Centre for Brain Repair, Cambridge, United Kingdom.
| |
Collapse
|
377
|
Twiss JL, van Minnen J. New insights into neuronal regeneration: the role of axonal protein synthesis in pathfinding and axonal extension. J Neurotrauma 2006; 23:295-308. [PMID: 16629617 DOI: 10.1089/neu.2006.23.295] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Protein synthesis in dendrites has become an accepted cellular mechanism that contributes to activity-dependent responses in the post-synaptic neuron. Although it was argued that protein synthesis does not occur in axons, early studies from a number of groups provided evidence for the presence of RNAs and active protein synthesis machinery in both invertebrate and vertebrate axons. Work over the past decade has confirmed these early findings and has proven the capability of axons to locally synthesize some of their own proteins. The functional significance of this localized protein synthesis remained largely unknown until recent years. Recent studies have shown that mRNA translation in developing and mature axons plays a role in axonal growth. In developing axons, protein synthesis allows the distal axon to autonomously respond to guidance cues by rapidly changing its direction of outgrowth. In addition, local proteolysis of axonal proteins contributes axonal guidance and growth cone initiation. This local synthesis and degradation of proteins are likely to provide novel insights into how growing axons navigate through their complex environment. In mature axons, injury triggers formation of a growth cone through localized protein synthesis, and moreover, in these injured axons locally synthesized proteins provide a retrogradely transported signal that can enhance regenerative responses. The intrinsic capability for axons to autonomously regulate local protein levels can be modulated by exogenous stimuli providing opportunities for enhancing regeneration. In this review, the concept of axonal protein synthesis is discussed from a historical perspective. Further, the implications of axonal protein synthesis and proteolysis for neural repair are considered.
Collapse
Affiliation(s)
- Jeffery L Twiss
- Nemours Biomedical Research, Alfred I duPont Hospital for Children, Wilmington, Delaware 19803, USA.
| | | |
Collapse
|
378
|
Niclou SP, Ehlert EME, Verhaagen J. Chemorepellent axon guidance molecules in spinal cord injury. J Neurotrauma 2006; 23:409-21. [PMID: 16629626 DOI: 10.1089/neu.2006.23.409] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Regenerating axons stop growing when they reach the border of the glial-fibrotic scar, presumably because they encounter a potent molecular barrier inhibiting growth cone advance. Chemorepulsive axon guidance molecules provide a non-permissive environment restricting and channeling axon growth in the developing nervous system. These molecules could also act as growth-inhibitory molecules in the regenerating nervous system. The receptors for repulsive guidance cues are expressed in the mature nervous system, suggesting that adult neurons are sensitive to the activity of developmentally active repulsive proteins. In this review, we summarize recent observations on semaphorins, ephrins, and slits in the injured brain and spinal cord, providing evidence that these proteins are major players in inhibiting axonal regeneration and establishing the glial-fibrotic scar.
Collapse
Affiliation(s)
- Simone P Niclou
- Netherlands Institute for Brain Research, Laboratory for Neuroregeneration, Amsterdam, The Netherlands.
| | | | | |
Collapse
|
379
|
Cao Z, Gao Y, Bryson JB, Hou J, Chaudhry N, Siddiq M, Martinez J, Spencer T, Carmel J, Hart RB, Filbin MT. The cytokine interleukin-6 is sufficient but not necessary to mimic the peripheral conditioning lesion effect on axonal growth. J Neurosci 2006; 26:5565-73. [PMID: 16707807 PMCID: PMC6675293 DOI: 10.1523/jneurosci.0815-06.2006] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Lesioning the peripheral branch of a dorsal root ganglion (DRG) neuron before injury of the central branch of the same neuron enables spontaneous regeneration of these spinal axons. This effect is cAMP and transcription dependent. Here, we show that the cytokine interleukin-6 (IL-6) is upregulated in DRG neurons after either a conditioning lesion or treatment with dibutyryl-cAMP. In culture, IL-6 allows neurons to grow in the presence of inhibitors of regeneration present in myelin. Importantly, intrathecal delivery of IL-6 to DRG neurons blocks inhibition by myelin both in vitro and in vivo, effectively mimicking the conditioning lesion. Blocking IL-6 signaling has no effect on the ability of cAMP to overcome myelin inhibitors. Consistent with this, IL-6-deficient mice respond to a conditioning lesion as effectively as wild-type mice. We conclude that IL-6 can mimic both the cAMP effect and the conditioning lesion effect but is not an essential component of either response.
Collapse
MESH Headings
- Animals
- Animals, Newborn
- Bucladesine/pharmacology
- CHO Cells
- Cells, Cultured
- Cricetinae
- Disease Models, Animal
- Female
- Ganglia, Spinal/cytology
- Ganglia, Spinal/drug effects
- Ganglia, Spinal/metabolism
- Growth Cones/drug effects
- Growth Cones/metabolism
- Growth Inhibitors/antagonists & inhibitors
- Growth Inhibitors/metabolism
- Interleukin-6/metabolism
- Interleukin-6/pharmacology
- Male
- Mice
- Mice, Knockout
- Myelin Proteins/antagonists & inhibitors
- Myelin Proteins/metabolism
- Nerve Regeneration/drug effects
- Nerve Regeneration/physiology
- Neurons, Afferent/cytology
- Neurons, Afferent/drug effects
- Neurons, Afferent/metabolism
- Peripheral Nerve Injuries
- Peripheral Nerves/cytology
- Peripheral Nerves/metabolism
- Rats
- Rats, Long-Evans
- Sciatic Neuropathy/drug therapy
- Sciatic Neuropathy/metabolism
- Sciatic Neuropathy/physiopathology
- Up-Regulation/drug effects
- Up-Regulation/physiology
Collapse
|
380
|
Tan AM, Colletti M, Rorai AT, Skene JHP, Levine JM. Antibodies against the NG2 proteoglycan promote the regeneration of sensory axons within the dorsal columns of the spinal cord. J Neurosci 2006; 26:4729-39. [PMID: 16672645 PMCID: PMC6674154 DOI: 10.1523/jneurosci.3900-05.2006] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The NG2 chondroitin sulfate proteoglycan inhibits axon growth in vitro. Levels of NG2 increase rapidly in the glial scars that form at sites of CNS injury, suggesting that NG2 may inhibit axon regeneration. To determine the functions of NG2, we infused mixtures of neutralizing or non-neutralizing anti-NG2 monoclonal antibodies into the dorsally transected adult rat spinal cord and analyzed the regeneration of ascending mechanosensory axons anatomically. At 1 week after injury, ascending sensory axons in control animals terminated caudal to the lesion within an area containing dense deposits of NG2 immunoreactivity. In animals treated with the neutralizing anti-NG2 antibodies, labeled axons penetrated the caudal border of the lesion and grew into and beyond the lesion center. The low intrinsic growth capacity of adult neurons may also limit the ability of damaged axons to regenerate. To enhance growth, we combined antibody treatment with a peripheral nerve conditioning lesion. After a conditioning lesion and treatment with control, non-neutralizing antibodies, many sensory axons grew into the lesion core. These axons did not grow past the rostral border of the lesion; rather, they grew along the dorsal surface of the spinal cord and within any remaining pieces of the dorsal roots. In contrast, combining a peripheral nerve conditioning lesion with neutralizing anti-NG2 antibodies resulted in sensory axon regeneration past the glial scar and into the white matter rostral to the injury site. The combinatorial approach used here that neutralizes extrinsic inhibition and increases intrinsic growth results in anatomically correct axon regeneration, a prerequisite for functional recovery.
Collapse
Affiliation(s)
- Andrew M Tan
- Department of Neurobiology and Behavior, State University of New York, Stony Brook, New York 11794, USA
| | | | | | | | | |
Collapse
|
381
|
Seijffers R, Allchorne AJ, Woolf CJ. The transcription factor ATF-3 promotes neurite outgrowth. Mol Cell Neurosci 2006; 32:143-54. [PMID: 16713293 DOI: 10.1016/j.mcn.2006.03.005] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Revised: 03/10/2006] [Accepted: 03/23/2006] [Indexed: 12/17/2022] Open
Abstract
Dorsal root ganglion (DRG) neurons regenerate after a peripheral nerve injury but not after injury to their axons in the spinal cord. A key question is which transcription factors drive the changes in gene expression that increase the intrinsic growth state of peripherally injured sensory neurons? A prime candidate is activating transcription factor-3 (ATF-3), a transcription factor that we find is induced in all DRG neurons after peripheral, but not central axonal injury. Moreover, we show in adult DRG neurons that a preconditioning peripheral, but not central axonal injury, increases their growth, correlating closely with the pattern of ATF-3 induction. Using viral vectors, we delivered ATF-3 to cultured adult DRG neurons and find that ATF-3 enhances neurite outgrowth. Furthermore, ATF-3 promotes long sparsely branched neurites. ATF-3 overexpression did not increase c-Jun expression. ATF-3 may contribute, therefore, to neurite outgrowth by orchestrating the gene expression responses in injured neurons.
Collapse
Affiliation(s)
- Rhona Seijffers
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | | | | |
Collapse
|
382
|
Affiliation(s)
- Lauren C Case
- Division of Research, Genentech Inc., 1 DNA Way, South San Francisco, California 94080, USA.
| | | |
Collapse
|
383
|
Regeneration and Repair. Dev Neurobiol 2006. [DOI: 10.1007/0-387-28117-7_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
384
|
Steinmetz MP, Horn KP, Tom VJ, Miller JH, Busch SA, Nair D, Silver DJ, Silver J. Chronic enhancement of the intrinsic growth capacity of sensory neurons combined with the degradation of inhibitory proteoglycans allows functional regeneration of sensory axons through the dorsal root entry zone in the mammalian spinal cord. J Neurosci 2006; 25:8066-76. [PMID: 16135764 PMCID: PMC6725461 DOI: 10.1523/jneurosci.2111-05.2005] [Citation(s) in RCA: 171] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Peripherally conditioned sensory neurons have an increased capacity to regenerate their central processes. However, even conditioned axons struggle in the presence of a hostile CNS environment. We hypothesized that combining an aggressive conditioning strategy with modification of inhibitory reactive astroglial-associated extracellular matrix could enhance regeneration. We screened potential treatments using a model of the dorsal root entry zone (DREZ). In this assay, a gradient of inhibitory chondroitin sulfate proteoglycans (CSPGs) stimulates formation of dystrophic end bulbs on adult sensory axons, which mimics regeneration failure in vivo. Combining inflammation-induced preconditioning of dorsal root ganglia in vivo before harvest, with chondroitinase ABC (ChABC) digestion of proteoglycans in vitro allows for significant regeneration across a once potently inhibitory substrate. We then assessed regeneration through the DREZ after root crush in adult rats receiving the combination treatment, ChABC, or zymosan pretreatment alone or no treatment. Regeneration was never observed in untreated animals, and only minimal regeneration occurred in the ChABC- and zymosan-alone groups. However, remarkable regeneration was observed in a majority of animals that received the combination treatment. Regenerated fibers established functional synapses, as demonstrated electrophysiologically by the presence of an H-reflex. Two different postlesion treatment paradigms in which the timing of both zymosan and ChABC administration were varied after injury were ineffective in promoting regeneration. Therefore, zymosan pretreatment, but not posttreatment, of the sensory ganglia, combined with ChABC modification of CSPGs, resulted in robust and functional regeneration of sensory axons through the DREZ after root injury.
Collapse
Affiliation(s)
- Michael P Steinmetz
- Department of Neurosurgery, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA
| | | | | | | | | | | | | | | |
Collapse
|
385
|
Abstract
Failure of severed adult CNS axons to regenerate could be attributed to both a reduced intrinsic capacity to grow and an heightened susceptibility to inhibitory factors of the CNS extracellular environment. A particularly interesting and useful paradigm for investigating CNS axonal regeneration is its enhancement at the CNS branch of dorsal root ganglion (DRG) neurons after conditional lesioning of their peripheral branch. Recent reports have implicated the involvement of two well-known signaling pathways utilizing separate transcription factors; the Cyclic AMP (cAMP) response element binding protein (CREB) and signal transducer and activator of transcription 3 (STAT3), in conditional lesioning. The former appears to be the pathway activated by neurotrophic factors and Bcl-2, while the latter is responsible for the neurogenic effect of cytokines [such as the leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) elevated at lesion sites]. Recent findings also augmented earlier notions that modulations of the activity of another class of cellular signaling intermediate, the conventional protein kinase C (PKC), could result in a contrasting growth response by CNS neurons to myelin-associated inhibitors. We discuss these signaling pathways and mechanisms, in conjunction with other recent reports of regeneration enhancement and also within the context of what is known about aiding regeneration of injured CNS axons.
Collapse
Affiliation(s)
- Felicia Yu Hsuan Teng
- Department of Biochemistry Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597
| | | |
Collapse
|
386
|
Marklund N, Fulp CT, Shimizu S, Puri R, McMillan A, Strittmatter SM, McIntosh TK. Selective temporal and regional alterations of Nogo-A and small proline-rich repeat protein 1A (SPRR1A) but not Nogo-66 receptor (NgR) occur following traumatic brain injury in the rat. Exp Neurol 2006; 197:70-83. [PMID: 16321384 PMCID: PMC2849132 DOI: 10.1016/j.expneurol.2005.08.029] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2005] [Revised: 07/26/2005] [Accepted: 08/11/2005] [Indexed: 01/12/2023]
Abstract
Axons show a poor regenerative capacity following traumatic central nervous system (CNS) injury, partly due to the expression of inhibitors of axonal outgrowth, of which Nogo-A is considered the most important. We evaluated the acute expression of Nogo-A, the Nogo-66 receptor (NgR) and the novel small proline-rich repeat protein 1A (SPRR1A, previously undetected in brain), following experimental lateral fluid percussion (FP) brain injury in rats. Immunofluorescence with antibodies against Nogo-A, NgR and SPRR1A was combined with antibodies against the neuronal markers NeuN and microtubule-associated protein (MAP)-2 and the oligodendrocyte marker RIP, while Western blot analysis was performed for Nogo-A and NgR. Brain injury produced a significant increase in Nogo-A expression in injured cortex, ipsilateral external capsule and reticular thalamus from days 1-7 post-injury (P < 0.05) compared to controls. Increased expression of Nogo-A was observed in both RIP- and NeuN positive (+) cells in the ipsilateral cortex, in NeuN (+) cells in the CA3 region of the hippocampus and reticular thalamus and in RIP (+) cells in white matter tracts. Alterations in NgR expression were not observed following traumatic brain injury (TBI). Brain injury increased the extent of SPRR1A expression in the ipsilateral cortex and the CA3 at all post-injury time-points in NeuN (+) cells. The marked increases in Nogo-A and SPRR1A in several important brain regions suggest that although inhibitors of axonal growth may be upregulated, the injured brain is also capable of expressing proteins promoting axonal outgrowth following TBI.
Collapse
Affiliation(s)
- Niklas Marklund
- Traumatic Brain Injury Laboratory, Department of Neurosurgery, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
| | | | | | | | | | | | | |
Collapse
|
387
|
Willis DE, Twiss JL. The evolving roles of axonally synthesized proteins in regeneration. Curr Opin Neurobiol 2006; 16:111-8. [PMID: 16418002 DOI: 10.1016/j.conb.2006.01.002] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Accepted: 01/06/2006] [Indexed: 11/19/2022]
Abstract
Work emerging during the past decade has shown that axons, similar to dendrites, are capable of autonomously generating new proteins through translation of localized mRNAs. Even in mammals, neurons maintain the ability to target mRNAs and translational machinery into the axonal compartment well into adulthood. The biological functions of axonal protein synthesis in adult neurons are just now being revealed, and recent studies indicate that locally synthesized proteins facilitate regeneration. Local translation, in addition to protein degradation, is needed for growth cone formation after axotomy, for generating a retrogradely transported injury signal, and then to help structurally maintain the growing axon. Regulation of axonal protein synthesis by exogenous stimuli might provide a means to facilitate regeneration for neuronal populations that normally show poor regenerative capacity in the adult nervous system.
Collapse
Affiliation(s)
- Dianna E Willis
- Nemours Biomedical Research, Alfred I duPont Hospital for Children, Wilmington, Delaware, USA
| | | |
Collapse
|
388
|
Hossain-Ibrahim MK, Rezajooi K, MacNally JK, Mason MRJ, Lieberman AR, Anderson PN. Effects of lipopolysaccharide-induced inflammation on expression of growth-associated genes by corticospinal neurons. BMC Neurosci 2006; 7:8. [PMID: 16433912 PMCID: PMC1403789 DOI: 10.1186/1471-2202-7-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2005] [Accepted: 01/24/2006] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Inflammation around cell bodies of primary sensory neurons and retinal ganglion cells enhances expression of neuronal growth-associated genes and stimulates axonal regeneration. We have asked if inflammation would have similar effects on corticospinal neurons, which normally show little response to spinal cord injury. Lipopolysaccharide (LPS) was applied onto the pial surface of the motor cortex of adult rats with or without concomitant injury of the corticospinal tract at C4. Inflammation around corticospinal tract cell bodies in the motor cortex was assessed by immunohistochemistry for OX42 (a microglia and macrophage marker). Expression of growth-associated genes c-jun, ATF3, SCG10 and GAP-43 was investigated by immunohistochemistry or in situ hybridisation. RESULTS Application of LPS induced a gradient of inflammation through the full depth of the motor cortex and promoted c-Jun and SCG10 expression for up to 2 weeks, and GAP-43 upregulation for 3 days by many corticospinal neurons, but had very limited effects on neuronal ATF3 expression. However, many glial cells in the subcortical white matter upregulated ATF3. LPS did not promote sprouting of anterogradely labelled corticospinal axons, which did not grow into or beyond a cervical lesion site. CONCLUSION Inflammation produced by topical application of LPS promoted increased expression of some growth-associated genes in the cell bodies of corticospinal neurons, but was insufficient to promote regeneration of the corticospinal tract.
Collapse
Affiliation(s)
- MK Hossain-Ibrahim
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - K Rezajooi
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - JK MacNally
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - MRJ Mason
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - AR Lieberman
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - PN Anderson
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| |
Collapse
|
389
|
Harvey PJ, Grochmal J, Tetzlaff W, Gordon T, Bennett DJ. An investigation into the potential for activity-dependent regeneration of the rubrospinal tract after spinal cord injury. Eur J Neurosci 2005; 22:3025-35. [PMID: 16367769 DOI: 10.1111/j.1460-9568.2005.04514.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We tested whether regeneration of transected rubrospinal tract (RST) axons is facilitated by a prolonged electrical stimulation of these axons. A peripheral nerve was grafted to the transected RST at the cervical level (C4/5) of adult rats, providing a permissive environment for regeneration of rubrospinal axons. Direct antidromic stimulation of the RST was applied immediately after grafting through a microwire inserted just rostral to the RST lesion, using a 1-h 20-Hz supramaximal stimulation protocol. Stimulation caused no direct damage to rubrospinal axons, and was sufficient to recruit the entire rubrospinal tract. In control animals that had a nerve graft and implanted microwire with no stimulation, there were 42.7 +/- 10.2 rubrospinal neurons regenerated into the graft at 8 weeks, as assessed by retrograde labelling. In test animals that were stimulated there were 28.2 +/- 7.4 back-labelled neurons, not significantly different from control, indicating that this stimulation did not improve the regenerative capacity of rubrospinal neurons. Furthermore, reverse-transcriptase polymerase chain reaction and in situ hybridization for brain-derived neurotrophic factor (BDNF) and/or growth-associated protein-43 (GAP-43) expression in rubrospinal neurons revealed no significant difference between stimulated and unstimulated groups at 48 h after injury, with either 1 or 8 h of stimulation. In summary, direct stimulation of the injured RST axons for the periods tested does not increase expression of GAP-43 and BDNF, and ultimately does not promote regeneration of these central nervous system axons.
Collapse
Affiliation(s)
- Philip J Harvey
- Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada T6G 2S2
| | | | | | | | | |
Collapse
|
390
|
Mills CD, Bitler JL, Woolf CJ. Role of the peripheral benzodiazepine receptor in sensory neuron regeneration. Mol Cell Neurosci 2005; 30:228-37. [PMID: 16099172 DOI: 10.1016/j.mcn.2005.07.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Revised: 07/13/2005] [Accepted: 07/15/2005] [Indexed: 11/25/2022] Open
Abstract
Peripheral benzodiazepine receptor (PBR) expression increases in small dorsal root ganglion (DRG) sensory neurons after peripheral nerve injury. To determine the functional significance of this induction, we evaluated the effects of PBR ligands on rodent sensory axon outgrowth. In vitro, Ro5-4864, a PBR agonist, enhanced outgrowth only of small peripherin-positive DRG neurons. When DRG cells were preconditioned into an active growth state by a prior peripheral nerve injury Ro5-4864 augmented and PK 11195, a PBR antagonist, blocked the injury-induced increased outgrowth. In vivo, Ro5-4864 increased the initiation of regeneration after a sciatic nerve crush injury and the number of GAP-43-positive axons in the distal nerve while PK 11195 inhibited the enhanced growth produced by a preconditioning lesion. These results show that PBR has a role in the early regenerative response of small caliber sensory axons, the preconditioning effect, and that PBR agonists enhance sensory axon regeneration.
Collapse
Affiliation(s)
- Charles D Mills
- Neural Plasticity Research Group, Massachusetts General Hospital and Harvard Medical School, 149 13th Street, Charlestown, MA 02129, USA.
| | | | | |
Collapse
|
391
|
Lenzlinger PM, Shimizu S, Marklund N, Thompson HJ, Schwab ME, Saatman KE, Hoover RC, Bareyre FM, Motta M, Luginbuhl A, Pape R, Clouse AK, Morganti-Kossmann C, McIntosh TK. Delayed inhibition of Nogo-A does not alter injury-induced axonal sprouting but enhances recovery of cognitive function following experimental traumatic brain injury in rats. Neuroscience 2005; 134:1047-56. [PMID: 15979242 DOI: 10.1016/j.neuroscience.2005.04.048] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2005] [Revised: 04/03/2005] [Accepted: 04/27/2005] [Indexed: 11/21/2022]
Abstract
Traumatic brain injury causes long-term neurological motor and cognitive deficits, often with limited recovery. The inability of CNS axons to regenerate following traumatic brain injury may be due, in part, to inhibitory molecules associated with myelin. One of these myelin-associated proteins, Nogo-A, inhibits neurite outgrowth in vitro, and inhibition of Nogo-A in vivo enhances axonal outgrowth and sprouting and improves outcome following experimental CNS insults. However, the involvement of Nogo-A in the neurobehavioral deficits observed in experimental traumatic brain injury remains unknown and was evaluated in the present study using the 11C7 monoclonal antibody against Nogo-A. Anesthetized, male Sprague-Dawley rats were subjected to either lateral fluid percussion brain injury of moderate severity (2.5-2.6 atm) or sham injury. Beginning 24 h post-injury, monoclonal antibody 11C7 (n=17 injured, n=6 shams included) or control Ab (IgG) (n=16 injured, n=5 shams included) was infused at a rate of 5 microl/h over 14 days into the ipsilateral ventricle using osmotic minipumps connected to an implanted cannula. Rats were assessed up to 4 weeks post-injury using tests for neurological motor function (composite neuroscore, and sensorimotor test of adhesive paper removal) and, at 4 weeks, cognition was assessed using the Morris water maze. Hippocampal CA3 pyramidal neuron damage and corticospinal tract sprouting, using an anterograde tracer (biotinylated dextran amine), were also evaluated. Brain injury significantly increased sprouting from the uninjured corticospinal tract but treatment with monoclonal antibody 11C7 did not further increase the extent of sprouting nor did it alter the extent of CA3 cell damage. Animals treated with 11C7 showed no improvement in neurologic motor deficits but did show significantly improved cognitive function at 4 weeks post-injury when compared with brain-injured, IgG-treated animals. To our knowledge, the present findings are the first to suggest that (1) traumatic brain injury induces axonal sprouting in the corticospinal tract and this sprouting may be independent of myelin-associated inhibitory factors and (2) that post-traumatic inhibition of Nogo-A may promote cognitive recovery unrelated to sprouting in the corticospinal tract or neuroprotective effects on hippocampal cell loss following experimental traumatic brain injury.
Collapse
Affiliation(s)
- P M Lenzlinger
- Traumatic Brain Injury Laboratory, Department of Neurosurgery, University of Pennsylvania, 105 Hayden Hall, 3320 Smith Walk, Philadelphia, PA 19104, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
392
|
Neumann S, Skinner K, Basbaum AI. Sustaining intrinsic growth capacity of adult neurons promotes spinal cord regeneration. Proc Natl Acad Sci U S A 2005; 102:16848-52. [PMID: 16275900 PMCID: PMC1283855 DOI: 10.1073/pnas.0508538102] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The peripheral axonal branch of primary sensory neurons readily regenerates after peripheral nerve injury, but the central branch, which courses in the dorsal columns of the spinal cord, does not. However, if a peripheral nerve is transected before a spinal cord injury, sensory neurons that course in the dorsal columns will regenerate, presumably because their intrinsic growth capacity is enhanced by the priming peripheral nerve lesion. As the effective priming lesion is made before the spinal cord injury it would clearly have no clinical utility, and unfortunately, a priming lesion made after a spinal cord injury results in an abortive regenerative response. Here, we show that two priming lesions, one made at the time of a spinal cord injury and a second 1 week after a spinal cord injury, in fact, promote dramatic regeneration, within and beyond the lesion. The first lesion, we hypothesize, enhances intrinsic growth capacity, and the second one sustains it, providing a paradigm for promoting CNS regeneration after injury.
Collapse
Affiliation(s)
- Simona Neumann
- Department of Anatomy, University of California, San Francisco, CA 94143, USA.
| | | | | |
Collapse
|
393
|
Hoang TX, Havton LA. A single re-implanted ventral root exerts neurotropic effects over multiple spinal cord segments in the adult rat. Exp Brain Res 2005; 169:208-17. [PMID: 16273401 DOI: 10.1007/s00221-005-0137-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2005] [Accepted: 07/11/2005] [Indexed: 12/20/2022]
Abstract
Spinal cord injuries, particularly traumatic injuries to the conus medullaris and cauda equina, are typically complex and involve multiple segmental levels. Implantation of avulsed ventral roots into the spinal cord as a repair strategy has been shown to be neuroprotective and promote axonal regeneration by spinal cord neurons into an implanted root. However, it is not well known over what distance in the spinal cord an implanted ventral root can exert its neurotropic effect. Here, we investigated whether an avulsed L6 ventral root acutely implanted into the rat spinal cord after a four level (L5-S2) unilateral ventral root avulsion injury may exert neurotropic effects on autonomic and motor neurons over multiple spinal cord segments at 6 weeks postoperatively. Using retrograde labeling techniques and stereological quantification methods, we demonstrate that autonomic and motor neurons from all four lesioned spinal cord segments, spanning more than an 8 mm rostro-caudal distance, reinnervated the one implanted root. The rostro-caudal distribution suggested a gradient of neurotropism, where the axotomized neurons closest to the implanted site had the highest probability of root reinnervation. These results suggest that implantation of a single ventral root may provide neurotropic effects to injured neurons at the site of lesion as well as in the adjacent spinal cord segments. Our findings may be of translational research interest for the development of surgical repair strategies after multi-level conus medullaris and cauda equina injuries, in which fewer ventral roots than spinal cord segments may be available for implantation.
Collapse
Affiliation(s)
- Thao X Hoang
- Department of Neurology and Brain Research Institute, David Geffen School of Medicine at UCLA, 710 Westwood Plaza, Los Angeles, CA 90095-1769, USA
| | | |
Collapse
|
394
|
Qiu J, Cafferty WBJ, McMahon SB, Thompson SWN. Conditioning injury-induced spinal axon regeneration requires signal transducer and activator of transcription 3 activation. J Neurosci 2005; 25:1645-53. [PMID: 15716400 PMCID: PMC6725934 DOI: 10.1523/jneurosci.3269-04.2005] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Sensory axons in the adult spinal cord do not regenerate after injury. This is essentially because of inhibitory components in the damaged CNS, such as myelin-associated inhibitors and the glial scar. However, if the sciatic nerve is axotomized before injury of the dorsal column, injured axons can regenerate a short distance in the spinal cord. Here, we show that sciatic nerve transection results in time-dependent phosphorylation and activation of the transcription factor, signal transducer and activator of transcription 3 (STAT3), in dorsal root ganglion (DRG) neurons. This effect is specific to peripheral injuries and does not occur when the dorsal column is crushed. Sustained perineural infusion of the Janus kinase 2 (JAK2) inhibitor AG490 to the proximal nerve stump can block STAT3 phosphorylation after sciatic nerve transection and results in reduced growth-associated protein 43 upregulation and compromised neurite outgrowth in vitro. Importantly, in vivo perineural infusion of AG490 also significantly attenuates dorsal column axonal regeneration in the adult spinal cord after a preconditioning sciatic nerve transection. We conclude that STAT3 activation is necessary for increased growth ability of DRG neurons and improved axonal regeneration in the spinal cord after a conditioning injury.
Collapse
Affiliation(s)
- Jin Qiu
- Wolfson Centre for Age-Related Diseases, Guy's, King's, and St. Thomas's School of Biomedical Science, King's College London, London SE1 1UL, United Kingdom
| | | | | | | |
Collapse
|
395
|
Zhang Y, Bo X, Schoepfer R, Holtmaat AJDG, Verhaagen J, Emson PC, Lieberman AR, Anderson PN. Growth-associated protein GAP-43 and L1 act synergistically to promote regenerative growth of Purkinje cell axons in vivo. Proc Natl Acad Sci U S A 2005; 102:14883-8. [PMID: 16195382 PMCID: PMC1253563 DOI: 10.1073/pnas.0505164102] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Indexed: 01/19/2023] Open
Abstract
Neuronal expression of growth-associated protein 43 (GAP-43) and the cell adhesion molecule L1 has been correlated with CNS axonal growth and regeneration, but it is not known whether expression of these molecules is necessary for axonal regeneration to occur. We have taken advantage of the fact that Purkinje cells do not express GAP-43 or L1 in adult mammals or regenerate axons into peripheral nerve grafts to test the importance of these molecules for axonal regeneration in vivo. Transgenic mice were generated in which Purkinje cells constitutively express L1 or both L1 and GAP-43 under the Purkinje cell-specific L7 promoter, and regeneration of Purkinje cell axons into peripheral nerve grafts implanted into the cerebellum was examined. Purkinje cells expressing GAP-43 or L1 showed minor enhancement of axonal sprouting. Purkinje cells expressing both GAP-43 and L1 showed more extensive axonal sprouting and axonal growth into the proximal portion of the graft. When a predegenerated nerve graft was implanted into double-transgenic mice, penetration of the graft by Purkinje cell axonal sprouts was strongly enhanced, and some axons grew along the entire intracerebral length of the graft (2.5-3.0 mm) and persisted for several months. The results demonstrate that GAP-43 and L1 coexpressed in Purkinje cells can act synergistically to switch these regeneration-incompetent CNS neurons into a regeneration-competent phenotype and show that coexpression of these molecules is a key regulator of the regenerative ability of intrinsic CNS neurons in vivo.
Collapse
Affiliation(s)
- Yi Zhang
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
| | | | | | | | | | | | | | | |
Collapse
|
396
|
Starkey ML, Barritt AW, Yip PK, Davies M, Hamers FPT, McMahon SB, Bradbury EJ. Assessing behavioural function following a pyramidotomy lesion of the corticospinal tract in adult mice. Exp Neurol 2005; 195:524-39. [PMID: 16051217 DOI: 10.1016/j.expneurol.2005.06.017] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Revised: 05/27/2005] [Accepted: 06/27/2005] [Indexed: 11/25/2022]
Abstract
We have developed a pyramidotomy model in mice to lesion the corticospinal tract at the level of the brainstem pyramidal tract, and evaluated the resultant impairments in motor function in a series of behavioural tests. Adult C57BL/6 mice received a unilateral pyramidotomy and a control group of mice underwent sham surgery. We studied the effects of this lesion on forepaw function using five behavioural paradigms, some of which have been widely used in rat studies but have not been fully explored in mice. The tests used were: a rearing test, which assesses forepaw use for weight support during spontaneous vertical exploration of a cylinder; a grid walking test, which assesses the ability to accurately place the forepaws during exploration of an elevated grid; a tape-removal test, which measures both sensory and motor function of the forepaw; a CatWalk automated gait analysis, which provides a number of quantitative measures including stride length and stride width during locomotion; and a staircase reaching task, which assesses skilled independent forepaw use. All tests revealed lesion effects on forepaw function with the tape removal, grid walking, rearing and CatWalk tests demonstrating robust effects throughout the testing period. The development of a pyramidotomy lesion model in mice, together with behavioural tests which can reliably measure functional impairments, will provide a valuable tool for assessing therapeutic strategies to promote regeneration and plasticity.
Collapse
Affiliation(s)
- Michelle L Starkey
- Neurorestoration Group, CARD Wolfson Wing, Hodgkin Building, King's College London, Guy's Campus, London Bridge, London SE1 IUL, UK
| | | | | | | | | | | | | |
Collapse
|
397
|
Baker KA, Hagg T. An adult rat spinal cord contusion model of sensory axon degeneration: the estrus cycle or a preconditioning lesion do not affect outcome. J Neurotrauma 2005; 22:415-28. [PMID: 15853460 DOI: 10.1089/neu.2005.22.415] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
A therapeutic strategy for acute spinal cord injury would be to reduce the progressive degeneration and disconnection of axons from their targets. Here, we describe a model to evaluate degeneration of the ascending sensory projections to the nuclei in the medulla following graded spinal cord contusions in adult female Sprague-Dawley rats. Cholera toxin B (CTB) labeling from the sciatic nerve of naive rats revealed effective labeling of the terminal fibers in the gracile nucleus at 3 days post-injection and a subpopulation of rapidly transporting fibers after 1 day. Seven days after contusions using the Infinite Horizon impactor the area of CTB-labeled terminal fibers had a negative correlation with increasing impact force. Moderate spinal contusions of around 150 kilodyne (kdyn or 0.15 x 10(-3) newton) caused a reduction to 40% in the fiber area which will enable the identification of protective as well as detrimental drugs and post-injury mechanisms. A preconditioning injury of the sciatic nerve reportedly can enhance growth of sensory axons but did not affect the terminal fiber area in the gracile nucleus. Estrogen and progesterone are protective in various systems and could therefore influence experimental outcomes when using females. However, the phase of the estrus cycle at the time of contusion or during the post-injury time did not affect the outcome of the contusion, indicating that female rats may be used without consideration of the estrus cycle. This model can readily be used to evaluate pharmacological agents for protection of sensory axons and pathophysiological mechanisms of their degeneration.
Collapse
Affiliation(s)
- K Adam Baker
- Departments of Neurological Surgery, Anatomical Sciences and Neurobiology, Kentucky Spinal Cord Injury Research Center, University of Louisville, 511 S. Floyd Street, Louisville, KY 40292, USA
| | | |
Collapse
|
398
|
Abstract
The lack of axonal growth after injury in the adult central nervous system (CNS) is due to several factors including the formation of a glial scar, the absence of neurotrophic factors, the presence of growth-inhibitory molecules associated with myelin and the intrinsic growth-state of the neurons. To date, three inhibitors have been identified in myelin: Myelin-Associated Glycoprotein (MAG), Nogo-A, and Oligodendrocyte-Myelin glycoprotein (OMgp). In previous studies we reported that MAG inhibits axonal regeneration by high affinity interaction (K(D) 8 nM) with the Nogo66 receptor (NgR) and activation of a p75 neurotrophin receptor (p75NTR)-mediated signaling pathway. Similar to other axon guidance molecules, MAG is bifunctional. When cultured on MAG-expressing cells, dorsal root ganglia neurons (DRG) older than post-natal day 4 (PND4) extend neurites 50% shorter on average than when cultured on control cells. In contrast, MAG promotes neurite outgrowth from DRG neurons from animals younger than PND4. The response switch, which is also seen in retinal ganglia (RGC) and Raphe nucleus neurons, is concomitant with a developmental decrease in the endogenous neuronal cAMP levels. We report that artificially increasing cAMP levels in older neurons can alter their growth-state and induce axonal growth in the presence of myelin-associated inhibitors.
Collapse
Affiliation(s)
- Marco Domeniconi
- Hunter College of City University of New York, Department of Biological Sciences, 695 Park Avenue Room 807N, New York, NY 10021, USA
| | | |
Collapse
|
399
|
Sasaki M, Lankford KL, Zemedkun M, Kocsis JD. Identified olfactory ensheathing cells transplanted into the transected dorsal funiculus bridge the lesion and form myelin. J Neurosci 2005; 24:8485-93. [PMID: 15456822 PMCID: PMC2605369 DOI: 10.1523/jneurosci.1998-04.2004] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Olfactory ensheathing cells (OECs) prepared from the olfactory bulbs of adult transgenic Sprague Dawley (SD) rats expressing green fluorescent protein (GFP) were transplanted into a dorsal spinal cord transection lesion of SD rats. Five weeks after transplantation, the cells survived within the lesion zone and oriented longitudinally along axons that bridged the transection site. Although the highest density of GFP cells was within the lesion zone, some cells distributed longitudinally outside of the lesion area. Myelinated axons spanning the lesion were observed in discrete bundles encapsulated by a cellular element. Electron micrographs of spinal cords immunostained with an anti-GFP antibody indicated that a majority of the peripheral-like myelinated axons were derived from donor OECs. Open-field locomotor behavior was significantly improved in the OEC transplantation group. Thus, transplanted OECs derived from the adult olfactory bulb can survive and orient longitudinally across a spinal cord transection site and form myelin. This pattern of repair is associated with improved locomotion.
Collapse
Affiliation(s)
- Masanori Sasaki
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut 06510, USA
| | | | | | | |
Collapse
|
400
|
Kerschensteiner M, Schwab ME, Lichtman JW, Misgeld T. In vivo imaging of axonal degeneration and regeneration in the injured spinal cord. Nat Med 2005; 11:572-7. [PMID: 15821747 DOI: 10.1038/nm1229] [Citation(s) in RCA: 406] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2004] [Accepted: 01/02/2005] [Indexed: 11/09/2022]
Abstract
The poor response of central axons to transection underlies the bleak prognosis following spinal cord injury. Here, we monitor individual fluorescent axons in the spinal cords of living transgenic mice over several days after spinal injury. We find that within 30 min after trauma, axons die back hundreds of micrometers. This acute form of axonal degeneration is similar in mechanism to the more delayed Wallerian degeneration of the disconnected distal axon, but acute degeneration affects the proximal and distal axon ends equally. In vivo imaging further shows that many axons attempt regeneration within 6-24 h after lesion. This growth response, although robust, seems to fail as a result of the inability of axons to navigate in the proper direction. These results suggest that time-lapse imaging of spinal cord injury may provide a powerful analytical tool for assessing the pathogenesis of spinal cord injury and for evaluating therapies that enhance regeneration.
Collapse
Affiliation(s)
- Martin Kerschensteiner
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, Massachusetts 02138, USA
| | | | | | | |
Collapse
|