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Benes JA, House KN, Burks FN, Conaway KP, Julien DP, Donley JP, Iyamu MA, McClellan AD. Regulation of axonal regeneration following spinal cord injury in the lamprey. J Neurophysiol 2017; 118:1439-1456. [PMID: 28469003 DOI: 10.1152/jn.00986.2016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 04/24/2017] [Accepted: 04/29/2017] [Indexed: 12/12/2022] Open
Abstract
Following rostral spinal cord injury (SCI) in larval lampreys, injured descending brain neurons, particularly reticulospinal (RS) neurons, regenerate their axons, and locomotor behavior recovers in a few weeks. However, axonal regeneration of descending brain neurons is mostly limited to relatively short distances, but the mechanisms for incomplete axonal regeneration are unclear. First, lampreys with rostral SCI exhibited greater axonal regeneration of descending brain neurons, including RS neurons, as well as more rapid recovery of locomotor muscle activity right below the lesion site, compared with animals with caudal SCI. In addition, following rostral SCI, most injured RS neurons displayed the "injury phenotype," whereas following caudal SCI, most injured neurons displayed normal electrical properties. Second, following rostral SCI, at cold temperatures (~4-5°C), axonal transport was suppressed, axonal regeneration and behavioral recovery were blocked, and injured RS neurons displayed normal electrical properties. Cold temperatures appear to prevent injured RS neurons from detecting and/or responding to SCI. It is hypothesized that following rostral SCI, injured descending brain neurons are strongly stimulated to regenerate their axons, presumably because of elimination of spinal synapses and reduced neurotrophic support. However, when these neurons regenerate their axons and make synapses right below the lesion site, restoration of neurotrophic support very likely suppress further axonal regeneration. In contrast, caudal SCI is a weak stimulus for axonal regeneration, presumably because of spared synapses above the lesion site. These results may have implications for mammalian SCI, which can spare synapses above the lesion site for supraspinal descending neurons and propriospinal neurons.NEW & NOTEWORTHY Lampreys with rostral spinal cord injury (SCI) exhibited greater axonal regeneration of descending brain neurons and more rapid recovery of locomotor muscle activity below the lesion site compared with animals with caudal SCI. In addition, following rostral SCI, most injured reticulospinal (RS) neurons displayed the "injury phenotype," whereas following caudal SCI, most injured neurons had normal electrical properties. We hypothesize that following caudal SCI, the spared synapses of injured RS neurons might limit axonal regeneration and behavioral recovery.
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Affiliation(s)
- Jessica A Benes
- Division of Biological Sciences, University of Missouri, Columbia, Missouri; and
| | - Kylie N House
- Division of Biological Sciences, University of Missouri, Columbia, Missouri; and
| | - Frank N Burks
- Division of Biological Sciences, University of Missouri, Columbia, Missouri; and
| | - Kris P Conaway
- Division of Biological Sciences, University of Missouri, Columbia, Missouri; and
| | - Donald P Julien
- Division of Biological Sciences, University of Missouri, Columbia, Missouri; and
| | - Jeffrey P Donley
- Division of Biological Sciences, University of Missouri, Columbia, Missouri; and
| | - Michael A Iyamu
- Division of Biological Sciences, University of Missouri, Columbia, Missouri; and
| | - Andrew D McClellan
- Division of Biological Sciences, University of Missouri, Columbia, Missouri; and .,Interdisciplinary Neuroscience Program, University of Missouri, Columbia, Missouri
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Benítez-Temiño B, Davis-López de Carrizosa MA, Morcuende S, Matarredona ER, de la Cruz RR, Pastor AM. Functional Diversity of Neurotrophin Actions on the Oculomotor System. Int J Mol Sci 2016; 17:E2016. [PMID: 27916956 PMCID: PMC5187816 DOI: 10.3390/ijms17122016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 11/24/2016] [Accepted: 11/25/2016] [Indexed: 11/16/2022] Open
Abstract
Neurotrophins play a principal role in neuronal survival and differentiation during development, but also in the maintenance of appropriate adult neuronal circuits and phenotypes. In the oculomotor system, we have demonstrated that neurotrophins are key regulators of developing and adult neuronal properties, but with peculiarities depending on each neurotrophin. For instance, the administration of NGF (nerve growth factor), BDNF (brain-derived neurotrophic factor) or NT-3 (neurotrophin-3) protects neonatal extraocular motoneurons from cell death after axotomy, but only NGF and BDNF prevent the downregulation in ChAT (choline acetyltransferase). In the adult, in vivo recordings of axotomized extraocular motoneurons have demonstrated that the delivery of NGF, BDNF or NT-3 recovers different components of the firing discharge activity of these cells, with some particularities in the case of NGF. All neurotrophins have also synaptotrophic activity, although to different degrees. Accordingly, neurotrophins can restore the axotomy-induced alterations acting selectively on different properties of the motoneuron. In this review, we summarize these evidences and discuss them in the context of other motor systems.
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Affiliation(s)
- Beatriz Benítez-Temiño
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | | | - Sara Morcuende
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | - Esperanza R Matarredona
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | - Rosa R de la Cruz
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
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Morcuende S, Muñoz-Hernández R, Benítez-Temiño B, Pastor AM, de la Cruz RR. Neuroprotective effects of NGF, BDNF, NT-3 and GDNF on axotomized extraocular motoneurons in neonatal rats. Neuroscience 2013; 250:31-48. [PMID: 23827308 DOI: 10.1016/j.neuroscience.2013.06.050] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 06/06/2013] [Accepted: 06/21/2013] [Indexed: 11/17/2022]
Abstract
Neurotrophic factors delivered from target muscles are essential for motoneuronal survival, mainly during development and early postnatal maturation. It has been shown that the disconnection between motoneurons and their innervated muscle by means of axotomy produces a vast neuronal death in neonatal animals. In the present work, we have evaluated the effects of different neurotrophic factors on motoneuronal survival after neonatal axotomy, using as a model the motoneurons innervating the extraocular eye muscles. With this purpose, neonatal rats were monocularly enucleated at the day of birth (postnatal day 0) and different neurotrophic treatments (NGF, BDNF, NT-3, GDNF and the mixture of BDNF+GDNF) were applied intraorbitally by means of a Gelfoam implant (a single dose of 5 μg of each factor). We first demonstrated that extraocular eye muscles of neonatal rats expressed these neurotrophic factors and therefore constituted a natural source of retrograde delivery for their innervating motoneurons. By histological and immunocytochemical methods we determined that all treatments significantly rescued extraocular motoneurons from axotomy-induced cell death. For the dose used, NGF and GDNF were the most potent survival factors for these motoneurons, followed by BDNF and lastly by NT-3. The simultaneous administration of BDNF and GDNF did not increase the survival-promoting effects above those obtained by GDNF alone. Interestingly, the rescue effects of all neurotrophic treatments persisted even 30 days after lesion. The administration of these neurotrophic factors, with the exception of NT-3, also prevented the loss of the cholinergic phenotype observed by 10 days after axotomy. At the dosage applied, NGF and GDNF were revealed again as the most effective neuroprotective agents against the axotomy-induced decrease in ChAT. Two remarkable findings highlighted in the present work that contrasted with other motoneuronal types after neonatal axotomy: first, the extremely high efficacy of NGF as a neuroprotective agent and, second, the long-lasting effects of neurotrophic administration on cell survival and ChAT expression in extraocular motoneurons.
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Affiliation(s)
- S Morcuende
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
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Talaverón R, Matarredona ER, de la Cruz RR, Pastor AM. Neural progenitor cell implants modulate vascular endothelial growth factor and brain-derived neurotrophic factor expression in rat axotomized neurons. PLoS One 2013; 8:e54519. [PMID: 23349916 PMCID: PMC3548797 DOI: 10.1371/journal.pone.0054519] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 12/12/2012] [Indexed: 12/27/2022] Open
Abstract
Axotomy of central neurons leads to functional and structural alterations which largely revert when neural progenitor cells (NPCs) are implanted in the lesion site. The new microenvironment created by NPCs in the host tissue might modulate in the damaged neurons the expression of a high variety of molecules with relevant roles in the repair mechanisms, including neurotrophic factors. In the present work, we aimed to analyze changes in neurotrophic factor expression in axotomized neurons induced by NPC implants. For this purpose, we performed immunofluorescence followed by confocal microscopy analysis for the detection of vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and nerve growth factor (NGF) on brainstem sections from rats with axotomy of abducens internuclear neurons that received NPC implants (implanted group) or vehicle injections (axotomized group) in the lesion site. Control abducens internuclear neurons were strongly immunoreactive to VEGF and BDNF but showed a weak staining for NT-3 and NGF. Comparisons between groups revealed that lesioned neurons from animals that received NPC implants showed a significant increase in VEGF content with respect to animals receiving vehicle injections. However, the immunoreactivity for BDNF, which was increased in the axotomized group as compared to control, was not modified in the implanted group. The modifications induced by NPC implants on VEGF and BDNF content were specific for the population of axotomized abducens internuclear neurons since the neighboring abducens motoneurons were not affected. Similar levels of NT-3 and NGF immunolabeling were obtained in injured neurons from axotomized and implanted animals. Among all the analyzed neurotrophic factors, only VEGF was expressed by the implanted cells in the lesion site. Our results point to a role of NPC implants in the modulation of neurotrophic factor expression by lesioned central neurons, which might contribute to the restorative effects of these implants.
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Affiliation(s)
- Rocío Talaverón
- Laboratorio de Fisiología y Plasticidad Neuronal, Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Esperanza R. Matarredona
- Laboratorio de Fisiología y Plasticidad Neuronal, Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Rosa R. de la Cruz
- Laboratorio de Fisiología y Plasticidad Neuronal, Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Angel M. Pastor
- Laboratorio de Fisiología y Plasticidad Neuronal, Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
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Morcuende S, Matarredona ER, Benítez-Temiño B, Muñoz-Hernández R, Pastor AM, de la Cruz RR. Differential regulation of the expression of neurotrophin receptors in rat extraocular motoneurons after lesion. J Comp Neurol 2011; 519:2335-52. [PMID: 21456016 DOI: 10.1002/cne.22630] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Neurotrophins acting through high-affinity tyrosine kinase receptors (trkA, trkB, and trkC) play a crucial role in regulating survival and maintenance of specific neuronal functions after injury. Adult motoneurons supplying extraocular muscles survive after disconnection from the target, but suffer dramatic changes in morphological and physiological properties, due in part to the loss of their trophic support from the muscle. To investigate the dependence of the adult rat extraocular motoneurons on neurotrophins, we examined trkA, trkB, and trkC mRNA expression after axotomy by in situ hybridization. trkA mRNA expression was detectable at low levels in unlesioned motoneurons, and its expression was downregulated 1 and 3 days after injury. Expression of trkB and trkC mRNAs was stronger, and after axotomy a simultaneous, but inverse regulation of both receptors was observed. Thus, whereas a considerable increase in trkB expression was seen about 2 weeks after axotomy, the expression of trkC mRNA had decreased at the same post-lesion period. Injured extraocular motoneurons also experienced an initial induction in expression of calcitonin gene-related peptide and a transient downregulation of cholinergic characteristics, indicating a switch in the phenotype from a transmitter-specific to a regenerative state. These results suggest that specific neurotrophins may contribute differentially to the survival and regenerative responses of extraocular motoneurons after lesion.
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Affiliation(s)
- Sara Morcuende
- Departamento de Fisiología y Zoología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
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Benítez-Temiño B, de la Cruz RR, Tena JJ, Pastor AM. Cerebellar grafting in the oculomotor system as a model to study target influence on adult neurons. ACTA ACUST UNITED AC 2004; 49:317-29. [PMID: 16111559 DOI: 10.1016/j.brainresrev.2004.09.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2004] [Revised: 08/31/2004] [Accepted: 09/15/2004] [Indexed: 11/19/2022]
Abstract
In the last decades, there have been many efforts directed to gain a better understanding on adult neuron-target cell relationships. Embryonic grafts have been used for the study of neural circuit rewiring. Thus, using several donor neuronal tissues, such as cerebellum or striatum, developing grafted cells have been shown to have the capability of substituting neural cell populations and establishing reciprocal connections with the host. In addition, different lesion paradigms have also led to a better understanding of target dependence in neuronal cells. Thus, for example, axotomy induces profound morphofunctional changes in adult neurons, including the loss of synaptic inputs and discharge alterations. These alterations are probably due to trophic factor loss in response to target disconnection. In this review, we summarize the different strategies performed to disconnect neurons from their targets, and the effects of target substitution, performed by tissue grafting, upon neural properties. Using the oculomotor system-and more precisely the abducens internuclear neurons-as a model, we describe herein the effects of disconnecting a population of central neurons from its natural target (i.e., the medial rectus motoneurons at the mesencephalic oculomotor nucleus). We also analyze target-derived influences in the structure and physiology of these neurons by using cerebellar embryonic grafts as a new target for the axotomized abducens internuclear neurons.
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Affiliation(s)
- Beatriz Benítez-Temiño
- Dept. Fisiología y Zoología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes, 6 41012 Sevilla, E-41012, Spain
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Benítez-Temiño B, Morcuende S, Mentis GZ, de la Cruz RR, Pastor AM. Expression of Trk receptors in the oculomotor system of the adult cat. J Comp Neurol 2004; 473:538-52. [PMID: 15116389 DOI: 10.1002/cne.20095] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We examined the expression of the three Trk receptors for neurotrophins (TrkA, TrkB, and TrkC) in the extraocular motor nuclei of the adult cat by using antibodies directed against the full-Trk proteins in combination with horseradish peroxidase retrograde tracing. The three receptors were present in all neuronal populations investigated, including abducens motoneurons and internuclear neurons, medial rectus motoneurons of the oculomotor nucleus, and trochlear motoneurons. They were also present in the vestibular and prepositus hypoglossi nuclei. TrkA, TrkB, and TrkC immunopositive cells were found in similar percentages in the oculomotor and in the trochlear nuclei. In the abducens nucleus, however, a significantly higher percentage of cells expressed TrkB than the other two receptors, among both motoneurons (81.8%) and internuclear neurons (88.4%). The percentages obtained for the three Trk receptors in identified neuronal populations pointed to the colocalization of two or three receptors in a large number of cells. We used confocal microscopy to elucidate the subcellular location of Trk receptors. In this case, abducens motoneurons and internuclear neurons were identified with antibodies against choline acetyltransferase and calretinin, respectively. We found a different pattern of staining for each neurotrophin receptor, suggesting the possibility that each receptor and its cognate ligand may use a different route for cellular signaling. Therefore, the expression of Trk receptors in oculomotor, trochlear, and abducens motoneurons, as well as abducens internuclear neurons, suggests that their associated neurotrophins may exert an influence on the normal operation of the oculomotor circuitry. The presence of multiple Trk receptors on individual cells indicates that they likely act in concert with each other to regulate distinct functions.
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Benítez-Temiño B, de la Cruz RR, Pastor AM. Grafting of a new target prevents synapse loss in abducens internuclear neurons induced by axotomy. Neuroscience 2003; 118:611-26. [PMID: 12710971 DOI: 10.1016/s0306-4522(03)00003-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The loss of afferent synaptic boutons is a prominent alteration induced by axotomy on adult central neurons. In this work we attempted to prove whether synapse loss could be reverted by reconnection with a new target. We severed the medial longitudinal fascicle of adult cats and then transplanted embryonic cerebellar primordia at the lesion site immediately after lesion. As previously shown, the transected axons from abducens internuclear neurons penetrate and reinnervate the graft [J Comp Neurol 444 (2002) 324]. By immunocytochemistry and electron microscopy we studied the synaptology of abducens internuclear neurons under three conditions: control, axotomy and transplant (2 months of survival time). Semithin sections of the abducens nucleus were immunostained against calretinin, to identify abducens internuclear neurons, and either synaptophysin (SF), to label synaptic terminals, or glial fibrillary acidic protein (GFAP) to detect the astrocytic reaction. Optical and linear density of SF and GFAP immunostaining were measured. Data revealed a significant decrease in the density of SF-labeled terminals with a parallel increase in GFAP-immunoreactive elements after axotomy. On the contrary, in the transplant group, the density of SF-labeled terminals was found similar to control, and the astrocytic reaction induced by lesion was significantly reduced. At the ultrastructural level, synaptic coverage and linear density of boutons were measured around the somata of abducens internuclear neurons. Whereas a significant reduction in both parameters was found after axotomy, cells of the transplant group received a normal density of synaptic endings. The ratio between F- and S-type boutons was found similar in the three groups. Therefore, these findings indicate that the grafting of a new target can prevent the loss of afferent synaptic boutons produced by the axotomy.
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Affiliation(s)
- B Benítez-Temiño
- Departamento de Fisiología y Zoología, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
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