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1.
Investigations into mechanisms that restrict the recovery of functions after an injury to the brain or the spinal cord have
led to the discovery of specific neurite growth inhibitory factors in the adult central nervous system (CNS) of mammals. Blocking
their growth-suppressive function resulted in disinhibition of axonal growth, i.e. growth of cultured neurons on inhibitory
CNS tissue in vitro and regeneration of injured axons in vivo. The enhanced regenerative and compensatory fibre growth was often accompanied by a substantial improvement in the functional
recovery after CNS injury. The first clinical studies to assess the therapeutic potential of compounds that neutralize growth
inhibitors or interfere with their downstream signalling are currently in progress. This review discusses recent advances
in the understanding of how the ‘founder molecule’ Nogo-A and other glialderived growth inhibitors restrict the regeneration
and repair of disrupted neuronal circuits, thus limiting the functional recovery after CNS injuries.
Received 5 April 2007; received after revision 28 September 2007; accepted 1 October 2007 相似文献
2.
Olfactory ensheathing cells promote neurite sprouting of injured axons in vitro by direct cellular contact and secretion of soluble factors 总被引:18,自引:0,他引:18
Chung RS Woodhouse A Fung S Dickson TC West AK Vickers JC Chuah MI 《Cellular and molecular life sciences : CMLS》2004,61(10):1238-1245
Olfactory ensheathing cells (OECs) represent an exciting possibility for promoting axonal regeneration within the injured spinal cord. A number of studies have indicated the ability of these cells to promote significant reactive sprouting of injured axons within the injured spinal cord, and in some cases restoration of functional abilities. However, the cellular and/or molecular mechanisms OECs use to achieve this are unclear. To investigate such mechanisms, we report for the first time the ability of OECs to promote post-injury neurite sprouting in an in vitro model of axonal injury. Using this model, we were able to differentiate between the direct and indirect mechanisms underlying the ability of OECs to promote neuronal recovery from injury. We noted that OECs appeared to act as a physical substrate for the growth of post-injury neurite sprouts. We also found that while post-injury sprouting was promoted most when OECs were allowed to directly contact injured neurons, physical separation using tissue culture inserts (1 mm pore size, permeable to diffusible factors but not cells) did not completely block the promoting properties of OECs, suggesting that they also secrete soluble factors which aid post-injury neurite sprouting. Furthermore, this in vitro model allowed direct observation of the cellular interactions between OECs and sprouting neurites using live-cell-imaging techniques. In summary, we found that OECs separately promote neurite sprouting by providing a physical substrate for growth and through the expression of soluble factors. Our findings provide new insight into the ability of OECs to promote axonal regeneration, and also indicate potential targets for manipulation of these cells to enhance their restorative ability.Received 19 January 2004; received after revision 8 March 2004: accepted 17 March 2004 相似文献
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4.
Hobson SA Bacon A Elliot-Hunt CR Holmes FE Kerr NC Pope R Vanderplank P Wynick D 《Cellular and molecular life sciences : CMLS》2008,65(12):1806-1812
The neuropeptide galanin is widely, but not ubiquitously, expressed in the adult nervous system. Its expression is markedly upregulated in many neuronal tissues after nerve injury or disease. Over the last 10 years we have demonstrated that the peptide plays a developmental survival role to subsets of neurons in the peripheral and central nervous systems with resulting phenotypic changes in neuropathic pain and cognition. Galanin also appears to play a trophic role to adult sensory neurons following injury, via activation of GalR2, by stimulating neurite outgrowth. Furthermore, galanin also plays a neuroprotective role to the hippocampus following excitotoxic injury, again mediated by activation of GalR2. In summary, these studies demonstrate that a GalR2 agonist might have clinical utility in a variety of human diseases that affect the nervous system. 相似文献
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6.
Involvement of Akt in neurite outgrowth 总被引:1,自引:1,他引:0
Danielle E. Read Adrienne M. Gorman 《Cellular and molecular life sciences : CMLS》2009,66(18):2975-2984
The regulation of neuronal differentiation and neurite outgrowth is essential during development of the nervous system and
is crucial in developing therapies to promote axon regeneration after nerve injury or in neurodegenerative diseases. The serine/threonine
kinase Akt has been well documented to promote neuronal survival. More recently Akt has also been revealed as key mediator
of several aspects of neurite outgrowth, including elongation, branching and calibre. Downstream of Akt, several substrates
have been identified that are likely to play key roles in Akt-mediated neurite outgrowth, such as glycogen synthase kinase
3β, peripherin, mammalian target of rapamycin and δ-catenin. The physical interaction between Akt and Hsp27, another protein
that has been linked with neurite outgrowth, may also be significant in the process of neurite outgrowth. This review will
unite and discuss the research to date that has examined the functionality of Akt in neuronal differentiation during development
and neurite outgrowth. 相似文献
7.
Meier S Bräuer AU Heimrich B Nitsch R Savaskan NE 《Cellular and molecular life sciences : CMLS》2004,61(9):1082-1094
Myelin is crucial for the stabilization of axonal projections in the developing and adult mammalian brain. However, myelin
components also act as a non-permissive and repellent substrate for outgrowing axons. Therefore, one major factor which accounts
for the lack of axonal regeneration in the mature brain is myelin. Here we report on the appearance of mature, fully myelinated
axons during hippocampal development and following entorhinal lesion with the myelin-specific marker Black Gold. Although
entorhinal axons enter the hippocampal formation at embryonic day 17, light and ultrastructural analysis revealed that mature
myelinated fibers in the hippocampus occur in the second postnatal week. During postnatal development, increasing numbers
of myelinated fibers appear and the distribution of myelinated fibers at postnatal day 25 was similar to that found in the
adult. After entorhinal cortex lesion, a specific anterograde denervation in the hippocampus takes place, accompanied by a
long-lasting loss of myelin. Quantitative analysis of myelin and myelin breakdown products at different time points after
lesion revealed a temporally close correlation to the degeneration and reorganization pha-ses in the hippocampus. In contrast,
electroconvulsive seizures resulted in brief demyelination and a faster recovery time course. In conclusion, we could show
that the appearance of mature axons in the hippocampus is temporally regulated during development. In the adult hippocampus,
demyelination was found after anterograde degeneration and also following seizures, suggesting that independent types of insult
lead to demyelination. Reappearing mature axons were found in the hippocampus following axonal sprouting. Therefore, our quantitative
analysis of mature axons and myelination effectively reflects the readjusted axonal density and possible electrophysiological
balance following lesion.
Received 22 December 2003; received after revision 11 February 2004; accepted 17 February 2004 相似文献
8.
Chung RS Fung SJ Leung YK Walker AK McCormack GH Chuah MI Vickers JC West AK 《Cellular and molecular life sciences : CMLS》2007,64(19-20):2716-2722
Metallothionein (MT) expression is rapidly up-regulated following CNS injury, and there is a strong correlation between the presence or absence of MTand improved or impaired (respectively) recovery from such trauma.We now report that a distinct subset of NG2-positive, GFAP-negative glial cells bordering the injury tract express MT following focal injury to the adult rat neocortex. To confirm the ability of these NG2 glial cells to express MT, we have isolated and cultured them and identified that they can express MT following stimulation with zinc. To investigate the functional importance of MT expression by NG2 glial cells, we plated cortical neurons onto these cells and found that expression of MT enhanced the permissivity of NG2 glial cells to neurite outgrowth. Our data suggest that expression of MT by NG2 glial cells may contribute to the overall permissiveness of these cells to axon regeneration. 相似文献
9.
The development of neuronal connectivity requires the growth of axons to their target region and the formation of dendritic
trees that extend into specific layers. Within the target region growth cones, the tips of extending axons are guided to finer
target fields including specific subcellular compartments where they form synapses. In this article we highlight recent progress
on molecular aspects of axonal subcellular target selection such as the axon initial segment or specific sublaminae of the
vertebrate retina. We then discuss the very recent progress on the molecular analysis of synapse formation in the central
nervous system, including the direction of differentiation into an inhibitory or excitatory synapse. Apparently, initial synaptic
contacts are structurally and functionally modulated by neuronal activity, raising the question how neuronal activity can
modify synaptic circuits. We therefore also focus on neural proteins that are up-regulated, secreted or converted by synaptic
activity and, thus, might represent molecular candidates for experience-driven refinement or remodeling of synaptic connections.
Received 5 July 2005; received after revision 19 August 2005; accepted 2 September 2005 相似文献
10.
Steinbeck JA Koch P Derouiche A Brüstle O 《Cellular and molecular life sciences : CMLS》2012,69(3):461-470
While the availability of pluripotent stem cells has opened new prospects for generating neural donor cells for nervous system
repair, their capability to integrate with adult brain tissue in a structurally relevant way is still largely unresolved.
We addressed the potential of human embryonic stem cell-derived long-term self-renewing neuroepithelial stem cells (lt-NES
cells) to establish axonal projections after transplantation into the adult rodent brain. Transgenic and species-specific
markers were used to trace the innervation pattern established by transplants in the hippocampus and motor cortex. In vitro,
lt-NES cells formed a complex axonal network within several weeks after the initiation of differentiation and expressed a
composition of surface receptors known to be instrumental in axonal growth and pathfinding. In vivo, these donor cells adopted
projection patterns closely mimicking endogenous projections in two different regions of the adult rodent brain. Hippocampal
grafts placed in the dentate gyrus projected to both the ipsilateral and contralateral pyramidal cell layers, while axons
of donor neurons placed in the motor cortex extended via the external and internal capsule into the cervical spinal cord and
via the corpus callosum into the contralateral cortex. Interestingly, acquisition of these region-specific projection profiles
was not correlated with the adoption of a regional phenotype. Upon reaching their destination, human axons established ultrastructural
correlates of synaptic connections with host neurons. Together, these data indicate that neurons derived from human pluripotent
stem cells are endowed with a remarkable potential to establish orthotopic long-range projections in the adult mammalian brain. 相似文献
11.
Neurotrophins and neuronal differentiation in the central nervous system 总被引:10,自引:0,他引:10
McAllister AK 《Cellular and molecular life sciences : CMLS》2001,58(8):1054-1060
The central nervous system requires the proper formation of exquisitely precise circuits to function properly. These neuronal
circuits are assembled during development by the formation of synaptic connections between hundreds of thousands of differentiating
neurons. For these circuits to form correctly, neurons must elaborate precisely patterned axonal and dendritic arbors. Although
the cellular and molecular mechanisms that guide neuronal differentiation and formation of connections remain mostly unknown,
the neurotrophins have emerged recently as attractive candidates for regulating neuronal differentiation in the developing
brain. The experiments reviewed here provide strong support for a bifunctional role for the neurotrophins in axonal and dendritic
growth and are consistent with the exciting possibility that the neurotrophins might mediate activity-dependent synaptic plasticity. 相似文献
12.
Windus LC Chehrehasa F Lineburg KE Claxton C Mackay-Sim A Key B St John JA 《Cellular and molecular life sciences : CMLS》2011,68(19):3233-3247
Axons of primary olfactory neurons are intimately associated with olfactory ensheathing cells (OECs) from the olfactory epithelium until the final targeting of axons within the olfactory bulb. However, little is understood about the nature and role of interactions between OECs and axons during development of the olfactory nerve pathway. We have used high resolution time-lapse microscopy to examine the growth and interactions of olfactory axons and OECs in vitro. Transgenic mice expressing fluorescent reporters in primary olfactory axons (OMP-ZsGreen) and ensheathing cells (S100ß-DsRed) enabled us to selectively analyse these cell types in explants of olfactory epithelium. We reveal here that rather than providing only a permissive substrate for axon growth, OECs play an active role in modulating the growth of pioneer olfactory axons. We show that the interactions between OECs and axons were dependent on lamellipodial waves on the shaft of OEC processes. The motility of OECs was mediated by GDNF, which stimulated cell migration and increased the apparent motility of the axons, whereas loss of OECs via laser ablation of the cells inhibited olfactory axon outgrowth. These results demonstrate that the migration of OECs strongly regulates the motility of axons and that stimulation of OEC motility enhances axon extension and growth cone activity. 相似文献
13.
T. Hubert S. Grimal P. Carroll A. Fichard-Carroll 《Cellular and molecular life sciences : CMLS》2009,66(7):1223-1238
Collagens are extracellular proteins characterized by a structure in triple helices. There are 28 collagen types which differ
in size, structure and function. Their architectural and functional roles in connective tissues have been widely assessed.
In the nervous system, collagens are rare in the vicinity of the neuronal soma, occupying mostly a “marginal” position, such
as the meninges, the basement membranes and the sensory end organs. In neural development, however, where various ECM molecules
are known to be determinant, recent studies indicate that collagens are no exception, participating in axonal guidance, synaptogenesis
and Schwann cell differentiation. Insights on collagens function in the brain have also been derived from neural pathophysiological
conditions. This review summarizes the significant advances which underscore the function and importance of collagens in the
nervous system.
Received 09 September 2008; received after revision 24 October 2008; accepted 28 October 2008 相似文献
14.
J Nguyen-Legros P Cesaro B Berger M Gay 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1979,288(17):1295-1298
The retrograde axonal transport of an iron-dextran complex was observed in neurons of the substantia nigra and of the intralaminar nuclei of the thalamus, after previous injection into the striatum. The histochemical demonstration of iron is simple and rapid, and can be combined with that of horseradish peroxidase, under precise conditions in the sequence of reactions. The iron-dextran complex revealed to be a valuable material for neuronal connectivity studies in the central nervous system. 相似文献
15.
C. Carobi 《Cellular and molecular life sciences : CMLS》1990,46(1):50-53
Summary The possible presence of neural sprouting in the afferent neurons of regenerated rat liver after hepatectomy was investigated bu retrograde transport of horesradish peroxidase. This experiment was carried out to see if the increase in hepatic parenchyma could provide an adequate stimulus for the sprouting precess. The study was limited to the vagal afferents, particularly the left ones, because they are the principal contributors to hepatic afferent innervation in the rat. The results show that neural sprouting does not occur in regenerated rat liver after 3 weeks In fact, the number of intensely labeled neurons in the left nodose ganglia of hepatectomized rats was significantly smaller than in controls. This could be due to a lessened availability of horseradish peroxidase to nerve terminals in hepatectomized and control animals. This could be a consequence of their possible distribution in hepatic areas not involved in the regenerative process. 相似文献
16.
G. Tear 《Cellular and molecular life sciences : CMLS》1999,55(11):1365-1376
A key feature of the central nervous system of most higher organisms is their bilateral symmetry about the midline. The specialised
cells that lie at the midline have an essential role in regulating the axon guidance decisions of both neurons that project
axons across the midline and those that project on one side. The midline cells produce both attractive and repellent short-
and long-range signals to guide axonal growth. The axons themselves express specific receptors that can be dynamically regulated
in response to midline-derived signals. In this way, axons extend toward or away from the midline and those that do cross
change their behaviour to respond to longitudinal signals on the contralateral side. 相似文献
17.
Degeneration of primary afferent central terminals (C-terminals) that contact neuronal soma in the substantia gelatinosa of the spinal dorsal horn was examined by electron microscopy 2 h after s.c. injection of capsaicin into newborn and adult mice. The C-terminals were small, dark, sinuous or slender terminals with clear synaptic vesicles in the early postnatal period. They are thought to develop into scalloped CI-terminals, surrounded by dendrites and a few axonal endings, forming synaptic glomeruli. The same type of nonglomerular terminals making presynaptic contacts with neuronal soma showed degeneration in both the newborn and adult animals, and were identified as capsaicin-sensitive CI-terminals. This finding suggests that capsaicin-sensitive C-fibers have a modulatory role on their own nociceptive input besides functioning in nociceptive transmission in the substantia gelatinosa. 相似文献
18.
C Carobi 《Experientia》1990,46(1):50-53
The possible presence of neural sprouting in the afferent neurons of regenerated rat liver after hepatectomy was investigated by retrograde transport of horseradish peroxidase. This experiment was carried out to see if the increase in hepatic parenchyma could provide an adequate stimulus for the sprouting process. The study was limited to the vagal afferents, particularly the left ones, because they are the principal contributors to hepatic afferent innervation in the rat. The results show that neural sprouting does not occur in regenerated rat liver after 3 weeks. In fact, the number of intensely labeled neurons in the left nodose ganglia of hepatectomized rats was significantly smaller than in controls. This could be due to a lessened availability of horseradish peroxidase to nerve terminals because of the increased non-innervated hepatic mass. There was no difference between right nodose ganglia neurons in hepatectomized and control animals. This could be a consequence of their possible distribution in hepatic areas not involved in the regenerative process. 相似文献
19.
Oxidative stress and hypoxia-like injury cause Alzheimer-type molecular abnormalities in central nervous system neurons 总被引:11,自引:0,他引:11
de la Monte SM Neely TR Cannon J Wands JR 《Cellular and molecular life sciences : CMLS》2000,57(10):1471-1481
Neuronal loss and neuritic/cytoskeletal lesions (synaptic disconnection and proliferation of dystrophic neurites) represent
major dementia-associated abnormalities in Alzheimer’s disease (AD). This study examined the role of oxidative stress as a
factor contributing to both the cell death and neuritic degeneration cascades in AD. Primary neuron cultures were treated
with H2O2 (9–90 μM) or desferrioxamine (2–25 μM) for 24 h and then analyzed for viability, mitochondrial mass, mitochondrial function,
and pro-apoptosis and sprouting gene expression. H2O2 treatment causes free-radical injury and desferrioxamine causes hypoxia-type injury without free radical generation. The
H2O2-treated cells exhibited sustained viability but neurite retraction, impaired mitochondrial function, increased levels of
the pro-apoptosis gene product CD95/Fas, reduced expression of N2J1-immunoreactive neuronal thread protein and synaptophysin,
and reduced distribution of mitochondria in neuritic processes. Desferrioxamine treatment resulted in dose-dependent neuronal
loss associated with impaired mitochondrial function, proliferation of neurites, and reduced expression of GAP-43, which has
a role in path-finding during neurite outgrowth. The results suggest that oxidative stress can cause neurodegeneration associated
with enhanced susceptibility to apoptosis due to activation of pro-apoptosis genes, neurite retraction (synaptic disconnection),
and impaired transport of mitochondria to cell processes where they are likely required for synaptic function. In contrast,
hypoxia-type injury causes neuronal loss with proliferation of neurites (sprouting), impaired mitochondrial function, and
reduced expression of molecules required to form and maintain synaptic connections. Since similar abnormalities occur in AD,
both oxidative stress and hypoxic injury can contribute to AD neurodegeneration.
Received 24 May 2000; received after revision 7 July 2000; accepted 27 July 2000 相似文献
20.
V. Auld 《Cellular and molecular life sciences : CMLS》1999,55(11):1377-1385
Growth cones experience many different cues in their journey to their final target. They can respond to a variety of attractive and repulsive cues that can be secreted or cellular. These cues are generated by a wide range of cell types. One subset of cells that play an important role in growth cone guidance are glial cells. Glia secrete guidance cues and express cellular cues on their surface that guide axonal outgrowth. In doing so, glia can act as intermediate targets in growth cone guidance, a process that is conserved between vertebrate and invertebrate nervous systems. Recent work in grasshopper, Drosophila and moth nervous system development has underscored the importance of the instructive role glia play during axonal outgrowth. 相似文献