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Neuron Dec 2013The spinal cord contains many descending and ascending longitudinal tracts whose development appears to be controlled by distinct guidance systems. We identified a...
The spinal cord contains many descending and ascending longitudinal tracts whose development appears to be controlled by distinct guidance systems. We identified a population of dorsal spinal neurons marked by coexpression of the transcription factor Zic2 and the guidance receptor EphA4. Zic2+;EphA4+ neurons are surrounded by mechanosensory terminals, suggesting innervation by mechanoreceptor afferents. Their axons form an ipsilateral ascending pathway that develops during embryogenesis and projects within the ventral aspect of the dorsal funiculus, the same location as the descending corticospinal tract (CST), which develops postnatally. Interestingly, the same guidance mechanism, namely, ephrinB3-induced EphA4 forward signaling, is required for the guidance of both ascending and descending axon tracts. Our analysis of conditional EphA4 mutant mice also revealed that the development of the dorsal funiculus occurs independently of EphA4 expression in descending CST axons and is linked to the distribution of Zic2+;EphA4+ spinal neurons and the formation of the ascending pathway.
Topics: Animals; Axons; Cell Tracking; Cells, Cultured; Central Nervous System; Embryonic Development; Ephrin-B3; Gene Expression Regulation, Developmental; Interneurons; Mice; Mice, Knockout; Mice, Transgenic; Neural Pathways; Posterior Horn Cells; Receptor, EphA4; Spinal Cord; Transcription Factors
PubMed: 24360544
DOI: 10.1016/j.neuron.2013.10.006 -
Clinical & Developmental Immunology 2013The glial scar formed by reactive astrocytes and axon growth inhibitors associated with myelin play important roles in the failure of axonal regeneration following...
The glial scar formed by reactive astrocytes and axon growth inhibitors associated with myelin play important roles in the failure of axonal regeneration following central nervous system (CNS) injury. Our laboratory has previously demonstrated that immunological demyelination of the CNS facilitates regeneration of severed axons following spinal cord injury. In the present study, we evaluate whether immunological demyelination is accompanied with astrogliosis. We compared the astrogliosis and macrophage/microglial cell responses 7 days after either immunological demyelination or a stab injury to the dorsal funiculus. Both lesions induced a strong activated macrophage/microglial cells response which was significantly higher within regions of immunological demyelination. However, immunological demyelination regions were not accompanied by astrogliosis compared to stab injury that induced astrogliosis which extended several millimeters above and below the lesions, evidenced by astroglial hypertrophy, formation of a glial scar, and upregulation of intermediate filaments glial fibrillary acidic protein (GFAP). Moreover, a stab or a hemisection lesion directly within immunological demyelination regions did not induced astrogliosis within the immunological demyelination region. These results suggest that immunological demyelination creates a unique environment in which astrocytes do not form a glial scar and provides a unique model to understand the putative interaction between astrocytes and activated macrophage/microglial cells.
Topics: Animals; Astrocytes; Cell Survival; Demyelinating Diseases; Female; Gliosis; Macrophage Activation; Macrophages; Microglia; Nerve Tissue Proteins; Rats; Spinal Cord Injuries
PubMed: 24319469
DOI: 10.1155/2013/812456 -
Cell Transplantation 2013Amyotrophic lateral sclerosis (ALS) is a fatal disease that involves the degeneration of cortical and spinal motor neurons. Mutant SOD1(G93A) rats constitute a good...
Amyotrophic lateral sclerosis (ALS) is a fatal disease that involves the degeneration of cortical and spinal motor neurons. Mutant SOD1(G93A) rats constitute a good animal model for this pathological condition. We have previously demonstrated that transplantation of neonatal olfactory ensheathing cells (OECs) into the dorsal funiculus of the spinal cord of mutant SOD1(G93A) transgenic rats increases the survival of spinal motor neurons and remyelinates the impaired axons through the pyramidal tract. In the present study, we examine whether intracranial cell implantation could also exert a similar effect on cortical motor neurons and on the lower motor neurons in the spinal cord. We injected OECs from the bulb of 7-day-old GFP green rats into the corona radiata of adult SOD1 mutant rats stereotaxically to observe any changes of the upper motor neurons as well as the lower motor neurons. We found that more motor neurons at both the motor cortices and ventral horns of the spinal cord survived in grafted ALS rats than in control rats. Prolonged survival and behavioral tests including a screen test, hind limb extension, rotarod, and gait control showed that the treated animals were better than the control group. This manuscript is published as part of the International Association of Neurorestoratology (IANR) supplement issue of Cell Transplantation.
Topics: Amyotrophic Lateral Sclerosis; Animals; Disease Models, Animal; Immunohistochemistry; Male; Motor Neurons; Olfactory Bulb; Rats; Rats, Sprague-Dawley; Superoxide Dismutase; Superoxide Dismutase-1
PubMed: 23993044
DOI: 10.3727/096368913X672208 -
Journal of Neurophysiology Oct 2013Transmission through descending pathways to lumbar motoneurons, although important for voluntary walking in humans and rats, has not been fully understood at the...
Transmission through descending pathways to lumbar motoneurons, although important for voluntary walking in humans and rats, has not been fully understood at the cellular level in contusion models. Major descending pathways innervating lumbar motoneurons include those at corticospinal tract (CST) and ventrolateral funiculus (VLF). We examined transmission and plasticity at synaptic pathways from dorsal (d)CST and VLF to individual motoneurons located in ventral horn and interneurons located in dorsomedial gray matter at lumbar segments after thoracic chronic contusion in adult anesthetized rats. To accomplish this, we used intracellular electrophysiological recordings and performed acute focal spinal lesions during the recordings. We directly demonstrate that after thoracic T10 chronic contusion the disrupted dCST axons spontaneously form new synaptic contacts with individual motoneurons, extending around the contusion cavity, through spared ventrolateral white matter. These detour synaptic connections are very weak, and strengthening these connections in order to improve function may be a target for therapeutic interventions after spinal cord injury (SCI). We found that degradation of scar-related chondroitin sulfate proteoglycans with the enzyme chondroitinase ABC (ChABC) combined with adeno-associated viral (AAV) vector-mediated prolonged delivery of neurotrophin NT-3 (AAV-NT3) strengthened these spontaneously formed connections in contused spinal cord. Moreover, ChABC/AAV-NT3 treatment induced the appearance of additional detour synaptic pathways innervating dorsomedial interneurons. Improved transmission in ChABC/AAV-NT3-treated animals was associated with increased immunoreactivity of 5-HT-positive fibers in lumbar dorsal and ventral horns. Improved locomotor function assessed with automated CatWalk highlights the physiological significance of these novel connections.
Topics: Animals; Chondroitin ABC Lyase; Contusions; Dependovirus; Female; Genetic Therapy; Interneurons; Locomotion; Motor Neurons; Neuronal Plasticity; Neurotrophin 3; Pyramidal Tracts; Rats; Rats, Sprague-Dawley; Spinal Cord Injuries; Synapses; Thoracic Injuries
PubMed: 23864374
DOI: 10.1152/jn.00427.2013 -
Scientific Reports 2013Spinal cord injury (SCI) is a severe condition leading to enduring motor deficits. When lesions are incomplete, promoting spinal cord plasticity might be a useful...
Spinal cord injury (SCI) is a severe condition leading to enduring motor deficits. When lesions are incomplete, promoting spinal cord plasticity might be a useful strategy to elicit functional recovery. Here we investigated whether long-term fluoxetine administration in the drinking water, a treatment recently demonstrated to optimize brain plasticity in several pathological conditions, promotes motor recovery in rats that received a C4 dorsal funiculus crush. We show that fluoxetine administration markedly improved motor functions compared to controls in several behavioral paradigms. The improved functional effects correlated positively with significant sprouting of intact corticospinal fibers and a modulation of the excitation/inhibition balance. Our results suggest a potential application of fluoxetine treatment as a non invasive therapeutic strategy for SCI-associated neuropathologies.
Topics: Animals; Disease Models, Animal; Fluoxetine; Gait; Male; Motor Activity; Motor Cortex; Neuronal Plasticity; Psychomotor Performance; Rats; Recovery of Function; Selective Serotonin Reuptake Inhibitors; Spinal Cord; Spinal Cord Injuries; Time Factors
PubMed: 23860568
DOI: 10.1038/srep02217 -
Stem Cell Research Sep 2013The loss of oligodendroglia and demyelination contributes to the lack of functional recovery after spinal cord injury. The transplantation of adult neural progenitor...
Bone morphogenetic proteins prevent bone marrow stromal cell-mediated oligodendroglial differentiation of transplanted adult neural progenitor cells in the injured spinal cord.
The loss of oligodendroglia and demyelination contributes to the lack of functional recovery after spinal cord injury. The transplantation of adult neural progenitor cells (NPCs) might be a promising strategy to replace oligodendroglia lost after injury, however only a very small proportion of grafted NPCs differentiate into oligodendroglia. The present study aimed to investigate whether co-transplantation of subventricular zone-derived NPCs with bone marrow stromal cells (BMSCs) will enhance oligodendroglial differentiation of NPCs. In vitro, oligodendroglial differentiation was strongly enhanced by co-cultivation of NPCs with BMSCs or BMSC-conditioned medium. For in vivo experiments, adult Fischer 344 rats underwent cervical dorsal funiculus transections, immediately followed by grafting of 5-bromo-2'-deoxyuridine (BrdU) pre-labeled syngeneic NPCs mixed with BMSCs isolated from adult bone marrow. Six weeks post-injury and grafting, BMSC-containing grafts filled the lesion cavity but did not enhance oligodendroglial differentiation of co-grafted NPCs. The failure of BMSCs to induce oligodendroglial differentiation in vivo coincided with a rapid upregulation of bone morphogenetic protein 2/4 (BMP2/4) around the injury site and in vitro data demonstrated that BMP2/4 can override the oligodendrogenic effects of BMSCs. Moreover, blocking BMP activity can rescue the effect of BMSCs on NPCs. Thus, neutralization of BMP or BMP signaling might be required to allow for BMSC-induced oligodendroglial differentiation of grafted NPCs in the injured spinal cord.
Topics: Animals; Bone Marrow Transplantation; Bone Morphogenetic Protein 2; Bone Morphogenetic Protein 4; Cell Differentiation; Female; Humans; Immunohistochemistry; Mesenchymal Stem Cell Transplantation; Mesenchymal Stem Cells; Neural Stem Cells; Oligodendroglia; Rats; Rats, Inbred F344; Rats, Sprague-Dawley; Rats, Transgenic; Spinal Cord Injuries
PubMed: 23770801
DOI: 10.1016/j.scr.2013.05.003 -
The Journal of Pain Aug 2013Neuropathic pain is frequently characterized by spontaneous pain (ie, pain at rest) and, in some cases, by cold- and touch-induced allodynia. Mechanisms underlying the...
UNLABELLED
Neuropathic pain is frequently characterized by spontaneous pain (ie, pain at rest) and, in some cases, by cold- and touch-induced allodynia. Mechanisms underlying the chronicity of neuropathic pain are not well understood. Rats received spinal nerve ligation (SNL) and were monitored for tactile and thermal thresholds. While heat hypersensitivity returned to baseline levels within approximately 35 to 40 days, tactile hypersensitivity was still present at 580 days after SNL. Tactile hypersensitivity at post-SNL day 60 (D60) was reversed by microinjection of 1) lidocaine; 2) a cholecystokinin 2 receptor antagonist into the rostral ventromedial medulla; or 3) dorsolateral funiculus lesion. Rostral ventromedial medulla lidocaine at D60 or spinal ondansetron, a 5-hydroxytryptamine 3 antagonist, at post-SNL D42 produced conditioned place preference selectively in SNL-treated rats, suggesting long-lasting spontaneous pain. Touch-induced FOS was increased in the spinal dorsal horn of SNL rats at D60 and prevented by prior dorsolateral funiculus lesion, suggesting that long-lasting tactile hypersensitivity depends upon spinal sensitization, which is mediated in part by descending facilitation, in spite of resolution of heat hypersensitivity.
PERSPECTIVE
These data suggest that spontaneous pain is present for an extended period of time and, consistent with likely actions of clinically effective drugs, is maintained by descending facilitation.
Topics: Afferent Pathways; Anesthetics, Local; Animals; Benzodiazepines; Conditioning, Operant; Disease Models, Animal; Hormone Antagonists; Hyperalgesia; Lidocaine; Male; Medulla Oblongata; Neuralgia; Oncogene Proteins v-fos; Ondansetron; Pain Measurement; Pain Threshold; Rats; Rats, Sprague-Dawley; Serotonin Antagonists; Spinal Nerves; Time Factors
PubMed: 23602267
DOI: 10.1016/j.jpain.2013.02.011 -
Journal of Neurotrauma Jun 2013Blocking the action of inhibitory molecules at sites of central nervous system injury has been proposed as a strategy to promote axonal regeneration and functional...
Blocking the action of inhibitory molecules at sites of central nervous system injury has been proposed as a strategy to promote axonal regeneration and functional recovery. We have previously shown that genetic deletion or competitive antagonism of EphA4 receptor activity promotes axonal regeneration and functional recovery in a mouse model of lateral hemisection spinal cord injury. Here we have assessed the effect of blocking EphA4 activation using the competitive antagonist EphA4-Fc in a rat model of thoracic contusive spinal cord injury. Using a ledged tapered balance beam and open-field testing, we observed significant improvements in recovery of locomotor function after EphA4-Fc treatment. Consistent with functional improvement, using high-resolution ex vivo magnetic resonance imaging at 16.4T, we found that rats treated with EphA4-Fc had a significantly increased cross-sectional area of the dorsal funiculus caudal to the injury epicenter compared with controls. Our findings indicate that EphA4-Fc promotes functional recovery following contusive spinal cord injury and provides further support for the therapeutic benefit of treatment with the competitive antagonist in acute cases of spinal cord injury.
Topics: Animals; Blotting, Western; Brain; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Female; Humans; Immunoglobulin Fc Fragments; Magnetic Resonance Imaging; Rats; Rats, Wistar; Receptor, EphA4; Recombinant Fusion Proteins; Recovery of Function; Spinal Cord Injuries; Transfection
PubMed: 23557244
DOI: 10.1089/neu.2012.2729 -
Respiratory Physiology & Neurobiology Mar 2013High frequency spinal cord stimulation (HF-SCS) is a method of inspiratory muscle activation resulting in phrenic motoneuron activation via stimulation of spinal cord...
High frequency spinal cord stimulation (HF-SCS) is a method of inspiratory muscle activation resulting in phrenic motoneuron activation via stimulation of spinal cord pathways. The specific pathways mediating this response, however, are unknown. The aim of this study was to assess the potential role of upper cervical (C1-C4) pre-phrenic interneurons (UCI) and localize the pathways in the thoracic spinal cord mediating activation of phrenic motoneurons during HF-SCS. In 7 anesthetized, spinalized (C1 level) dogs, HF-SCS was applied at the T2 level. Diaphragm EMG, inspired volume and airway pressure generation were monitored before and following sequential spinal cord sections at the C4 and C8 levels. Section at the C4 level and dorsal columns at C8 resulted in no significant changes. However, lateral funiculi section (C8 level) resulted in significant reductions in each parameter. We conclude that during upper thoracic HF-SCS, the phrenic motoneuron pools are activated via spinal pathways located in the lateral funiculus but UCI are not involved.
Topics: Animals; Diaphragm; Dogs; Electric Stimulation; Intercostal Muscles; Interneurons; Phrenic Nerve; Spinal Cord; Thoracic Vertebrae
PubMed: 23261850
DOI: 10.1016/j.resp.2012.12.003 -
PloS One 2012Glutamate is the main excitatory neurotransmitter involved in spinal cord circuits in vertebrates, but in most groups the distribution of glutamatergic spinal neurons is...
Glutamate is the main excitatory neurotransmitter involved in spinal cord circuits in vertebrates, but in most groups the distribution of glutamatergic spinal neurons is still unknown. Lampreys have been extensively used as a model to investigate the neuronal circuits underlying locomotion. Glutamatergic circuits have been characterized on the basis of the excitatory responses elicited in postsynaptic neurons. However, the presence of glutamatergic neurochemical markers in spinal neurons has not been investigated. In this study, we report for the first time the expression of a vesicular glutamate transporter (VGLUT) in the spinal cord of the sea lamprey. We also study the distribution of glutamate in perikarya and fibers. The largest glutamatergic neurons found were the dorsal cells and caudal giant cells. Two additional VGLUT-positive gray matter populations, one dorsomedial consisting of small cells and another one lateral consisting of small and large cells were observed. Some cerebrospinal fluid-contacting cells also expressed VGLUT. In the white matter, some edge cells and some cells associated with giant axons (Müller and Mauthner axons) and the dorsolateral funiculus expressed VGLUT. Large lateral cells and the cells associated with reticulospinal axons are in a key position to receive descending inputs involved in the control of locomotion. We also compared the distribution of glutamate immunoreactivity with that of γ-aminobutyric acid (GABA) and glycine. Colocalization of glutamate and GABA or glycine was observed in some small spinal cells. These results confirm the glutamatergic nature of various neuronal populations, and reveal new small-celled glutamatergic populations, predicting that some glutamatergic neurons would exert complex actions on postsynaptic neurons.
Topics: Animals; Glycine; Immunohistochemistry; In Situ Hybridization; Lampreys; Microscopy, Fluorescence; Neurons; Spinal Cord; Vesicular Glutamate Transport Proteins; gamma-Aminobutyric Acid
PubMed: 23110124
DOI: 10.1371/journal.pone.0047898