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1.
Dev Dyn ; 250(9): 1340-1357, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-33347679

RESUMO

BACKGROUND: Slits (1-3) and their Robo (1-3) receptors play multiple non-neuronal roles in development, including in development of muscle, heart and mammary gland. Previous work has demonstrated expression of Slit and Robo family members during limb development, where their functions are unclear. RESULTS: In situ hybridisation confirmed strong expression of Slit2, Slit3, Robo1, and Robo2 throughout mouse limb and joint development. No expression of Slit1 or Robo3 was detected. Analysis of Slit1/2 or Slit3 knockout mice revealed normal limb development. In contrast, locally blocking Slit signaling though grafting of cells expressing a dominant-negative Robo2 construct in the proximo-central region of developing chicken limb buds caused significant shortening of the humerus. CONCLUSIONS: These findings demonstrate an essential role for Slit/Robo signaling in regulating bone length during chicken limb development.


Assuntos
Proteínas do Tecido Nervoso , Receptores Imunológicos , Animais , Galinhas , Úmero/metabolismo , Proteínas de Membrana/metabolismo , Camundongos , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Receptores Imunológicos/genética , Receptores Imunológicos/metabolismo , Transdução de Sinais/genética
2.
Glia ; 69(2): 235-254, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-32697392

RESUMO

Schwann cells within the peripheral nervous system possess a remarkable regenerative potential. Current research shows that peripheral nerve-associated Schwann cells possess the capacity to promote repair of multiple tissues including peripheral nerve gap bridging, skin wound healing, digit tip repair as well as tooth regeneration. One of the key features of the specialized repair Schwann cells is that they become highly motile. They not only migrate into the area of damaged tissue and become a key component of regenerating tissue but also secrete signaling molecules to attract macrophages, support neuronal survival, promote axonal regrowth, activate local mesenchymal stem cells, and interact with other cell types. Currently, the importance of migratory Schwann cells in tissue regeneration is most evident in the case of a peripheral nerve transection injury. Following nerve transection, Schwann cells from both proximal and distal nerve stumps migrate into the nerve bridge and form Schwann cell cords to guide axon regeneration. The formation of Schwann cell cords in the nerve bridge is key to successful peripheral nerve repair following transection injury. In this review, we first examine nerve bridge formation and the behavior of Schwann cell migration in the nerve bridge, and then discuss how migrating Schwann cells direct regenerating axons into the distal nerve. We also review the current understanding of signals that could activate Schwann cell migration and signals that Schwann cells utilize to direct axon regeneration. Understanding the molecular mechanism of Schwann cell migration could potentially offer new therapeutic strategies for peripheral nerve repair.


Assuntos
Axônios , Traumatismos dos Nervos Periféricos , Humanos , Regeneração Nervosa , Nervos Periféricos , Células de Schwann
3.
Glia ; 69(10): 2391-2403, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34115425

RESUMO

Peripheral nerve injury triggers sequential phenotype alterations in Schwann cells, which are critical for axonal regeneration. Long noncoding RNAs (lncRNAs) are long transcripts without obvious coding potential. It has been reported that lncRNAs participate in diverse biological processes and diseases. However, the role of lncRNA in Schwann cells and peripheral nerve regeneration is unclear. Here, we identified an lncRNA, loc680254, which is upregulated in rat sciatic nerve after peripheral nerve injury. The loc680254 knockdown inhibits Schwann cell proliferation, enhances apoptosis, and hinders cell cycle, while loc680254 overexpression has the opposite effect. Mechanically, we found that loc680254 might act as a microRNA sponge to regulate the expression of mitosis-related gene, spindle and kinetochore associated complex subunit 1 (Ska1) and proline/serine-rich coiled-coil 1 (Psrc1). Silencing of Psrc1 or Ska1 attenuates the effect of loc680254 overexpression on Schwann cell proliferation. Finally, we repaired the rat sciatic nerve gap with chitosan scaffolds loaded with loc680254-overexpressing Schwann cells and evaluated axon regeneration and functional recovery. Our results indicated that loc680254 is a new potential modulator for Schwann cell proliferation, which could be targeted to develop novel therapeutic strategies for peripheral nerve repair.


Assuntos
Proteínas Cromossômicas não Histona , MicroRNAs , Traumatismos dos Nervos Periféricos , Fosfoproteínas , RNA Longo não Codificante , Nervo Isquiático , Animais , Axônios/metabolismo , Proliferação de Células/genética , MicroRNAs/genética , MicroRNAs/metabolismo , Regeneração Nervosa/fisiologia , Traumatismos dos Nervos Periféricos/metabolismo , Ratos , Ratos Sprague-Dawley , Células de Schwann/metabolismo , Nervo Isquiático/lesões , Nervo Isquiático/metabolismo
4.
Development ; 144(17): 3114-3125, 2017 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-28743796

RESUMO

Correct myelination is crucial for the function of the peripheral nervous system. Both positive and negative regulators within the axon and Schwann cell function to ensure the correct onset and progression of myelination during both development and following peripheral nerve injury and repair. The Sox2 transcription factor is well known for its roles in the development and maintenance of progenitor and stem cell populations, but has also been proposed in vitro as a negative regulator of myelination in Schwann cells. We wished to test fully whether Sox2 regulates myelination in vivo and show here that, in mice, sustained Sox2 expression in vivo blocks myelination in the peripheral nerves and maintains Schwann cells in a proliferative non-differentiated state, which is also associated with increased inflammation within the nerve. The plasticity of Schwann cells allows them to re-myelinate regenerated axons following injury and we show that re-myelination is also blocked by Sox2 expression in Schwann cells. These findings identify Sox2 as a physiological regulator of Schwann cell myelination in vivo and its potential to play a role in disorders of myelination in the peripheral nervous system.


Assuntos
Macrófagos/metabolismo , Bainha de Mielina/metabolismo , Nervos Periféricos/metabolismo , Fatores de Transcrição SOXB1/metabolismo , Células de Schwann/metabolismo , Animais , Biomarcadores/metabolismo , Caderinas/metabolismo , Proliferação de Células , Proteína 2 de Resposta de Crescimento Precoce/metabolismo , Proteínas de Fluorescência Verde/metabolismo , Camundongos Transgênicos , Atividade Motora , Condução Nervosa , Traumatismos dos Nervos Periféricos/metabolismo , Traumatismos dos Nervos Periféricos/patologia , Nervos Periféricos/patologia , Nervos Periféricos/ultraestrutura , Proteínas Proto-Oncogênicas c-jun/metabolismo , Ratos , Recuperação de Função Fisiológica , Células de Schwann/patologia , Transgenes , beta Catenina/metabolismo
5.
J Neurochem ; 141(1): 37-47, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-27973735

RESUMO

Myelination in the peripheral nervous system (PNS) is controlled by both positive and negative regulators within Schwann cells to ensure timely onset and correct myelin thickness for saltatory conduction by neurons. Transcription factors such as Sox10, octamer-binding transcription factor 6 (Oct6) and Krox20 form a positive regulatory network, whereas negative regulators such as cJun and Sox2 oppose myelination in Schwann cells. The role of the p38 MAPK pathway has been studied in PNS myelination, but its precise function remains unclear, with both positive and negative effects of p38 activity reported upon both myelination and processes of nerve repair. To clarify the role of p38 MAPK in the PNS, we have analysed mice with a Schwann cell-specific ablation of the major p38 isoform, p38alpha. In line with previous findings of an inhibitory role for p38 MAPK, we observe acceleration of post-natal myelination in p38alpha null nerves, a delay in myelin down-regulation following injury, together with a small increase in levels of re-myelination following injury. Finally we explored roles for p38alpha in controlling axonal regeneration and functional repair following PNS injury and observe that loss of p38alpha function in Schwann cells does not appear to affect these processes as previously reported. These studies therefore provide further proof for a role of p38 MAPK signalling in the control of myelination by Schwann cells in the PNS, but do not show an apparent role for signalling by this MAP kinase in Schwann cells controlling other elements of Wallerian degeneration and functional repair following injury. Cover Image for this issue: doi: 10.1111/jnc.13793.


Assuntos
Proteína Quinase 14 Ativada por Mitógeno/fisiologia , Fibras Nervosas Mielinizadas/enzimologia , Traumatismos dos Nervos Periféricos/enzimologia , Nervos Periféricos/enzimologia , Recuperação de Função Fisiológica/fisiologia , Células de Schwann/enzimologia , Animais , Animais Recém-Nascidos , Células Cultivadas , Feminino , Masculino , Camundongos , Fibras Nervosas Mielinizadas/patologia , Traumatismos dos Nervos Periféricos/patologia , Nervos Periféricos/patologia , Ratos , Células de Schwann/patologia
6.
Int J Mol Sci ; 18(3)2017 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-28245592

RESUMO

Netrin-1 was the first axon guidance molecule to be discovered in vertebrates and has a strong chemotropic function for axonal guidance, cell migration, morphogenesis and angiogenesis. It is a secreted axon guidance cue that can trigger attraction by binding to its canonical receptors Deleted in Colorectal Cancer (DCC) and Neogenin or repulsion through binding the DCC/Uncoordinated (Unc5) A-D receptor complex. The crystal structures of Netrin-1/receptor complexes have recently been revealed. These studies have provided a structure based explanation of Netrin-1 bi-functionality. Netrin-1 and its receptor are continuously expressed in the adult nervous system and are differentially regulated after nerve injury. In the adult spinal cord and optic nerve, Netrin-1 has been considered as an inhibitor that contributes to axon regeneration failure after injury. In the peripheral nervous system, Netrin-1 receptors are expressed in Schwann cells, the cell bodies of sensory neurons and the axons of both motor and sensory neurons. Netrin-1 is expressed in Schwann cells and its expression is up-regulated after peripheral nerve transection injury. Recent studies indicated that Netrin-1 plays a positive role in promoting peripheral nerve regeneration, Schwann cell proliferation and migration. Targeting of the Netrin-1 signaling pathway could develop novel therapeutic strategies to promote peripheral nerve regeneration and functional recovery.


Assuntos
Fatores de Crescimento Neural/metabolismo , Regeneração Nervosa , Transdução de Sinais , Proteínas Supressoras de Tumor/metabolismo , Animais , Movimento Celular , Expressão Gênica , Humanos , Fatores de Crescimento Neural/química , Netrina-1 , Nervo Óptico/fisiologia , Traumatismos dos Nervos Periféricos/genética , Traumatismos dos Nervos Periféricos/metabolismo , Traumatismos dos Nervos Periféricos/patologia , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Multimerização Proteica , Receptores de Imunoglobulina Polimérica/metabolismo , Células de Schwann/metabolismo , Medula Espinal/metabolismo , Traumatismos da Medula Espinal/genética , Traumatismos da Medula Espinal/metabolismo , Traumatismos da Medula Espinal/patologia , Proteínas Supressoras de Tumor/química
7.
Brain ; 136(Pt 2): 549-63, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23413263

RESUMO

Loss of the Merlin tumour suppressor causes abnormal de-differentiation and proliferation of Schwann cells and formation of schwannoma tumours in patients with neurofibromatosis type 2. Within the mature peripheral nerve the normal development, differentiation and maintenance of myelinating and non-myelinating Schwann cells is regulated by a network of transcription factors that include SOX10, OCT6 (now known as POU3F1), NFATC4 and KROX20 (also known as Egr2). We have examined for the first time how their regulation of Schwann cell development is disrupted in primary human schwannoma cells. We find that induction of both KROX20 and OCT6 is impaired, whereas enforced expression of KROX20 drives both myelin gene expression and cell cycle arrest in Merlin-null cells. Importantly, we show that human schwannoma cells have reduced expression of SOX10 protein and messenger RNA. Analysis of mouse SOX10-null Schwann cells shows they display many of the characteristics of human schwannoma cells, including increased expression of platelet derived growth factor receptor beta (PDGFRB) messenger RNA and protein, enhanced proliferation, increased focal adhesions and schwannoma-like morphology. Correspondingly, reintroduction of SOX10 into human Merlin-null cells restores the ability of these cells to induce KROX20 and myelin protein zero (MPZ), localizes NFATC4 to the nucleus, reduces cell proliferation and suppresses PDGFRB expression. Thus, we propose that loss of the SOX10 protein, which is vital for normal Schwann cell development, is also key to the pathology of Merlin-null schwannoma tumours.


Assuntos
Técnicas de Silenciamento de Genes , Neurilemoma/genética , Neurofibromatose 2/genética , Neurofibromina 2/deficiência , Fenótipo , Fatores de Transcrição SOXE/deficiência , Animais , Células Cultivadas , Humanos , Camundongos , Camundongos Transgênicos , Neurilemoma/metabolismo , Neurilemoma/patologia , Neurofibromatose 2/metabolismo , Neurofibromatose 2/patologia , Neurofibromina 2/genética , Fatores de Transcrição SOXE/fisiologia
8.
Mol Cell Neurosci ; 49(3): 341-50, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22306864

RESUMO

Formation of a functional nervous system requires neurons to migrate to the correct place within the developing brain. Tangentially migrating neurons are guided by a leading process which extends towards the target and is followed by the cell body. How environmental cues are coupled to specific cytoskeletal changes to produce and guide leading process growth is unknown. One such cytoskeletal modulator is drebrin, an actin-binding protein known to induce protrusions in many cell types and be important for regulating neuronal morphology. Using the migration of oculomotor neurons as a model, we have shown that drebrin is necessary for the generation and guidance of the leading process. In the absence of drebrin, leading processes are not formed and cells fail to migrate although axon growth and pathfinding appear grossly unaffected. Conversely, when levels of drebrin are elevated the leading processes turn away from their target and as a result the motor neuron cell bodies move along abnormal paths within the brain. The aberrant trajectories were highly reproducible suggesting that drebrin is required to interpret specific guidance cues. The axons and growth cones of these neurons display morphological changes, particularly increased branching and filopodial number but despite this they extend along normal developmental pathways. Collectively these results show that drebrin is initially necessary for the formation of a leading process and subsequently for this to respond to navigational signals and grow in the correct direction. Furthermore, we have shown that the actions of drebrin can be segregated within individual motor neurons to direct their migration independently of axon guidance.


Assuntos
Movimento Celular/fisiologia , Proteínas dos Microfilamentos/metabolismo , Neurônios/metabolismo , Neuropeptídeos/metabolismo , Axônios/metabolismo , Axônios/patologia , Diferenciação Celular/fisiologia , Cones de Crescimento/metabolismo , Cones de Crescimento/patologia , Proteínas dos Microfilamentos/fisiologia , Neurônios/citologia , Pseudópodes/metabolismo
9.
Glia ; 60(9): 1269-78, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22532290

RESUMO

Pax-3 is a paired domain transcription factor that plays many roles during vertebrate development. In the Schwann cell lineage, Pax-3 is expressed at an early stage in Schwann cells precursors of the embryonic nerve, is maintained in the nonmyelinating cells of the adult nerve, and is upregulated in Schwann cells after peripheral nerve injury. Consistent with this expression pattern, Pax-3 has previously been shown to play a role in repressing the expression of the myelin basic protein gene in Schwann cells. We have studied the role of Pax-3 in Schwann cells and have found that it controls not only the regulation of cell differentiation but also the survival and proliferation of Schwann cells. Pax-3 expression blocks both the induction of Oct-6 and Krox-20 (K20) by cyclic AMP and completely inhibits the ability of K20, the physiological regulator of myelination in the peripheral nervous system, to induce myelin gene expression in Schwann cells. In contrast to other inhibitors of myelination, we find that Pax-3 represses myelin gene expression in a c-Jun-independent manner. In addition to this, we find that Pax-3 expression alone is sufficient to inhibit the induction of apoptosis by TGFß1 in Schwann cells. Expression of Pax-3 is also sufficient to induce the proliferation of Schwann cells in the absence of added growth factors and to reverse K20-induced exit from the cell cycle. These findings indicate new roles for the Pax-3 transcription factor in controlling the differentiation and proliferation of Schwann cells during development and after peripheral nerve injury.


Assuntos
Diferenciação Celular/fisiologia , Proliferação de Células , Fatores de Transcrição Box Pareados/metabolismo , Células de Schwann/metabolismo , Animais , Apoptose/genética , Plexo Braquial/citologia , Plexo Braquial/metabolismo , Ciclo Celular/fisiologia , Proteína 2 de Resposta de Crescimento Precoce/genética , Proteína 2 de Resposta de Crescimento Precoce/metabolismo , Regulação da Expressão Gênica , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Bainha de Mielina/genética , Bainha de Mielina/metabolismo , Fator 6 de Transcrição de Octâmero/genética , Fator 6 de Transcrição de Octâmero/metabolismo , Fator de Transcrição PAX3 , Fatores de Transcrição Box Pareados/genética , Proteínas Proto-Oncogênicas c-jun/genética , Proteínas Proto-Oncogênicas c-jun/metabolismo , Ratos , Células de Schwann/citologia , Nervo Isquiático/citologia , Nervo Isquiático/metabolismo
10.
Front Cell Neurosci ; 15: 676515, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34955748

RESUMO

Advances in single-cell RNA sequencing technologies and bioinformatics methods allow for both the identification of cell types in a complex tissue and the large-scale gene expression profiling of various cell types in a mixture. In this report, we analyzed a single-cell RNA sequencing (scRNA-seq) dataset for the intact adult mouse sciatic nerve and examined cell-type specific transcription factor expression and activity during peripheral nerve homeostasis. In total, we identified 238 transcription factors expressed in nine different cell types of intact mouse sciatic nerve. Vascular smooth muscle cells have the lowest number of transcription factors expressed with 17 transcription factors identified. Myelinating Schwann cells (mSCs) have the highest number of transcription factors expressed, with 61 transcription factors identified. We created a cell-type specific expression map for the identified 238 transcription factors. Our results not only provide valuable information about the expression pattern of transcription factors in different cell types of adult peripheral nerves but also facilitate future studies to understand the function of key transcription factors in the peripheral nerve homeostasis and disease.

11.
Front Cell Neurosci ; 15: 624826, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33828460

RESUMO

The advances in single-cell RNA sequencing technologies and the development of bioinformatics pipelines enable us to more accurately define the heterogeneity of cell types in a selected tissue. In this report, we re-analyzed recently published single-cell RNA sequencing data sets and provide a rationale to redefine the heterogeneity of cells in both intact and injured mouse peripheral nerves. Our analysis showed that, in both intact and injured peripheral nerves, cells could be functionally classified into four categories: Schwann cells, nerve fibroblasts, immune cells, and cells associated with blood vessels. Nerve fibroblasts could be sub-clustered into epineurial, perineurial, and endoneurial fibroblasts. Identified immune cell clusters include macrophages, mast cells, natural killer cells, T and B lymphocytes as well as an unreported cluster of neutrophils. Cells associated with blood vessels include endothelial cells, vascular smooth muscle cells, and pericytes. We show that endothelial cells in the intact mouse sciatic nerve have three sub-types: epineurial, endoneurial, and lymphatic endothelial cells. Analysis of cell type-specific gene changes revealed that Schwann cells and endoneurial fibroblasts are the two most important cell types promoting peripheral nerve regeneration. Analysis of communication between these cells identified potential signals for early blood vessel regeneration, neutrophil recruitment of macrophages, and macrophages activating Schwann cells. Through this analysis, we also report appropriate marker genes for future single cell transcriptome data analysis to identify cell types in intact and injured peripheral nerves. The findings from our analysis could facilitate a better understanding of cell biology of peripheral nerves in homeostasis, regeneration, and disease.

12.
Front Cell Neurosci ; 15: 743532, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34720881

RESUMO

CD146 is cell adhesion molecule and is implicated in a variety of physiological and pathological processes. However, the involvement of CD146 in peripheral nerve regeneration has not been studied yet. Here, we examine the spatial and temporal expression pattern of CD146 in injured mouse sciatic nerve via high-throughput data analysis, RT-PCR and immunostaining. By microarray data analysis and RT-PCR validation, we show that CD146 mRNA is significantly up-regulated in the nerve bridge and in the distal nerve stump following mouse sciatic nerve transection injury. By single cell sequencing data analysis and immunostaining, we demonstrate that CD146 is up-regulated in Schwann cells and cells associated with blood vessels following mouse peripheral nerve injury. Bioinformatic analysis revealed that CD146 not only has a key role in promoting of blood vessel regeneration but also regulates cell migration. The biological function of CD146 in Schwann cells was further investigated by knockdown of CD146 in rat primary Schwann cells. Functional assessments showed that knockdown of CD146 decreases viability and proliferation of Schwann cells but increases Schwann cell migration. Collectively, our findings imply that CD146 could be a key cell adhesion molecule that is up-regulated in injured peripheral nerves to regulate peripheral nerve regeneration.

13.
Front Cell Neurosci ; 15: 688243, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34744629

RESUMO

Following peripheral nerve injury, transcription factors upregulated in the distal nerve play essential roles in Schwann cell reprogramming, fibroblast activation and immune cell function to create a permissive distal nerve environment for axonal regrowth. In this report, we first analysed four microarray data sets to identify transcription factors that have at least twofold upregulation in the mouse distal nerve stump at day 3 and day 7 post-injury. Next, we compared their relative mRNA levels through the analysis of an available bulk mRNA sequencing data set at day 5 post-injury. We then investigated the expression of identified TFs in analysed single-cell RNA sequencing data sets for the distal nerve at day 3 and day 9 post-injury. These analyses identified 55 transcription factors that have at least twofold upregulation in the distal nerve following mouse sciatic nerve injury. Expression profile for the identified 55 transcription factors in cells of the distal nerve stump was further analysed on the scRNA-seq data. Transcription factor network and functional analysis were performed in Schwann cells. We also validated the expression pattern of Jun, Junb, Runx1, Runx2, and Sox2 in the mouse distal nerve stump by immunostaining. The findings from our study not only could be used to understand the function of key transcription factors in peripheral nerve regeneration but also could be used to facilitate experimental design for future studies to investigate the function of individual TFs in peripheral nerve regeneration.

14.
Neural Regen Res ; 15(5): 948-958, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31719262

RESUMO

The Slit family of axon guidance cues act as repulsive molecules for precise axon pathfinding and neuronal migration during nervous system development through interactions with specific Robo receptors. Although we previously reported that Slit1-3 and their receptors Robo1 and Robo2 are highly expressed in the adult mouse peripheral nervous system, how this expression changes after injury has not been well studied. Herein, we constructed a peripheral nerve injury mouse model by transecting the right sciatic nerve. At 14 days after injury, quantitative real-time polymerase chain reaction was used to detect mRNA expression of Slit1-3 and Robo1-2 in L4-5 spinal cord and dorsal root ganglia, as well as the sciatic nerve. Immunohistochemical analysis was performed to examine Slit1-3, Robo1-2, neurofilament heavy chain, F4/80, and vimentin in L4-5 spinal cord, L4 dorsal root ganglia, and the sciatic nerve. Co-expression of Slit1-3 and Robo1-2 in L4 dorsal root ganglia was detected by in situ hybridization. In addition, Slit1-3 and Robo1-2 protein expression in L4-5 spinal cord, L4 dorsal root ganglia, and sciatic nerve were detected by western blot assay. The results showed no significant changes of Slit1-3 or Robo1-2 mRNA expression in the spinal cord within 14 days after injury. In the dorsal root ganglion, Slit1-3 and Robo1-2 mRNA expression were initially downregulated within 4 days after injury; however, Robo1-2 mRNA expression returned to the control level, while Slit1-3 mRNA expression remained upregulated during regeneration from 4-14 days after injury. In the sciatic nerve, Slit1-3 and their receptors Robo1-2 were all expressed in the proximal nerve stump; however, Slit1, Slit2, and Robo2 were barely detectable in the nerve bridge and distal nerve stump within 14 days after injury. Slit3 was highly ex-pressed in macrophages surrounding the nerve bridge and slightly downregulated in the distal nerve stump within 14 days after injury. Robo1 was upregulated in vimentin-positive cells and migrating Schwann cells inside the nerve bridge. Robo1 was also upregulated in Schwann cells of the distal nerve stump within 14 days after injury. Our findings indicate that Slit3 is the major ligand expressed in the nerve bridge and distal nerve stump during peripheral nerve regeneration, and Slit3/Robo signaling could play a key role in peripheral nerve repair after injury. This study was approved by Plymouth University Animal Welfare Ethical Review Board (approval No. 30/3203) on April 12, 2014.

15.
Neural Regen Res ; 15(1): 6-9, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31535634

RESUMO

The peripheral nervous system has an astonishing ability to regenerate following a compression or crush injury; however, the potential for full repair following a transection injury is much less. Currently, the major clinical challenge for peripheral nerve repair come from long gaps between the proximal and distal nerve stumps, which prevent regenerating axons reaching the distal nerve. Precise axon targeting during nervous system development is controlled by families of axon guidance molecules including Netrins, Slits, Ephrins and Semaphorins. Several recent studies have indicated key roles of Netrin1, Slit3 and EphrinB2 signalling in controlling the formation of new nerve bridge tissue and precise axon regeneration after peripheral nerve transection injury. Inside the nerve bridge, nerve fibroblasts express EphrinB2 while migrating Schwann cells express the receptor EphB2. EphrinB2/EphB2 signalling between nerve fibroblasts and migrating Schwann cells is required for Sox2 upregulation in Schwann cells and the formation of Schwann cell cords within the nerve bridge to allow directional axon growth to the distal nerve stump. Macrophages in the outermost layer of the nerve bridge express Slit3 while migrating Schwann cells and regenerating axons express the receptor Robo1; within Schwann cells, Robo1 expression is also Sox2-dependent. Slit3/Robo1 signalling is required to keep migrating Schwann cells and regenerating axons inside the nerve bridge. In addition to the Slit3/Robo1 signalling system, migrating Schwann cells also express Netrin1 and regenerating axons express the DCC receptor. It appears that migrating Schwann cells could also use Netrin1 as a guidance cue to direct regenerating axons across the peripheral nerve gap. Engineered neural tissues have been suggested as promising alternatives for the repair of large peripheral nerve gaps. Therefore, understanding the function of classic axon guidance molecules in nerve bridge formation and their roles in axon regeneration could be highly beneficial in developing engineered neural tissue for more effective peripheral nerve repair.

16.
Front Cell Neurosci ; 14: 237, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32848626

RESUMO

The fibroblast growth factor (FGF) family polypeptides play key roles in promoting tissue regeneration and repair. FGF5 is strongly up-regulated in Schwann cells of the peripheral nervous system following injury; however, a role for FGF5 in peripheral nerve regeneration has not been shown up to now. In this report, we examined the expression of FGF5 and its receptors FGFR1-4 in Schwann cells of the mouse sciatic nerve following injury, and then measured the effects of FGF5 treatment upon cultured primary rat Schwann cells. By microarray and mRNA sequencing data analysis, RT-PCR, qPCR, western blotting and immunostaining, we show that FGF5 is highly up-regulated in Schwann cells of the mouse distal sciatic nerve following injury, and FGFR1 and FGFR2 are highly expressed in Schwann cells of the peripheral nerve both before and following injury. Using cultured primary rat Schwann cells, we show that FGF5 inhibits ERK1/2 MAP kinase activity but promotes rapid Schwann cell migration and adhesion via the upregulation of N-cadherin. Thus, FGF5 is an autocrine regulator of Schwann cells to regulate Schwann cell migration and adhesion.

17.
Curr Med Sci ; 40(3): 434-443, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32681248

RESUMO

Progressive memory loss and cognitive impairment are the main clinical manifestations of Alzheimer's disease (AD). Currently, there is no effective drug available for the treatment of AD. Previous studies have demonstrated that the cognitive impairment of AD is associated with oxidative stress and the inhibition of AKT and ERK phosphorylation. Grape seed proanthocyanidin extract (GSPE) has been shown to have strong antioxidant effect and can protect the nervous system from oxidative stress damage. This study aimed to investigate the protective effect of GSPE on the cognitive and synaptic impairments of AD using a sporadic AD rat model induced by intracerebroventricular (ICV) injection of streptozotocin (STZ) (ICV-STZ). Rats were treated with GSPE (50, 100, or 200 mg/kg every day) by intragastrical (ig.) administration for continuous 7 weeks, and ICV-STZ (3 mg/kg) was performed on the first day and third day of week 5. Learning and memory abilities were assessed by the Morris water maze (MWM) test at week 8. After behavioral test, hippocampal long-term potentiation (LTP) was recorded, and the levels of malondialdehyde (MDA), superoxide dismutases (SOD), glutathione (GSH) and the protein expression of AKT and ERK were measured in the hippocampus and cerebral cortex of rats. Our study revealed that ICV-STZ significantly impaired the working learning ability and hippocampal LTP of rats, significantly increased the levels of MDA, and decreased the activity of SOD and GSH in the hippocampus and cerebral cortex. In contrast, GSPE treatment prevented the impairment of cognitive function and hippocampal LTP induced by ICV-STZ, decreased the level of MDA, and increased the level of SOD and GSH. Furthermore, Western blot results showed that GSPE treatment could prevent the loss of AKT and ERK activities in the hippocampus and cerebral cortex induced by ICV-STZ. Our findings demonstrate that GSPE treatment could ameliorate the impairment of cognitive ability and hippocampal synaptic plasticity in a rat model of sporadic AD by inhibiting oxidative stress and preserving AKT and ERK activities. Therefore, GSPE may be an effective agent for the treatment of cognitive deficits associated with sporadic AD.


Assuntos
Disfunção Cognitiva/tratamento farmacológico , Extrato de Sementes de Uva/farmacologia , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Proantocianidinas/farmacologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Estreptozocina/farmacologia , Doença de Alzheimer/induzido quimicamente , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/metabolismo , Animais , Antioxidantes/fisiologia , Cognição/efeitos dos fármacos , Disfunção Cognitiva/metabolismo , Modelos Animais de Doenças , Glutationa/metabolismo , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Malondialdeído/metabolismo , Aprendizagem em Labirinto/efeitos dos fármacos , Memória/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Superóxido Dismutase/metabolismo
18.
Neuropeptides ; 79: 102000, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31864679

RESUMO

The neuropeptide galanin functions via three G-protein coupled receptors, Gal1-3-R. Both Gal1-R and 2-R are involved in pain signaling at the spinal level. Here a Gal2-R-EGFP transgenic (TG) mouse was generated and studied in pain tests and by characterizing Gal2-R expression in both sensory ganglia and spinal cord. After peripheral spared nerve injury, mechanical allodynia developed and was ipsilaterally similar between wild type (WT) and TG mice. A Gal2-R-EGFP-positive signal was primarily observed in small and medium-sized dorsal root ganglion (DRG) neurons and in spinal interneurons and processes. No significant difference in size distribution of DRG neuronal profiles was found between TG and WT mice. Both percentage and fluorescence intensity of Gal2-R-EGFP-positive neuronal profiles were overall significantly upregulated in ipsilateral DRGs as compared to contralateral DRGs. There was an ipsilateral reduction in substance P-positive and calcitonin gene-related peptide (CGRP)-positive neuronal profiles, and this reduction was more pronounced in TG as compared to WT mice. Moreover, Gal2-R-EGFP partly co-localized with three pain-related neuropeptides, CGRP, neuropeptide Y and galanin, both in intact and injured DRGs, and with galanin also in local neurons in the superficial dorsal horn. Taken together, the present results provide novel information on the localization and phenotype of DRG and spinal neurons expressing the second galanin receptor, Gal2-R, and on phenotypic changes following peripheral nerve injury. Gal2-R may also be involved in autoreceptor signaling.


Assuntos
Peptídeo Relacionado com Gene de Calcitonina/metabolismo , Gânglios Espinais/metabolismo , Neurônios/metabolismo , Medula Espinal/metabolismo , Animais , Camundongos Transgênicos , Neurônios Aferentes/metabolismo , Neuropeptídeo Y/metabolismo , Neuropeptídeos/metabolismo , Substância P/metabolismo
19.
Front Mol Neurosci ; 12: 308, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31920539

RESUMO

While it is proposed that interaction between Schwann cells and axons is key for successful nerve regeneration, the behavior of Schwann cells migrating into a nerve gap following a transection injury and how migrating Schwann cells interact with regenerating axons within the nerve bridge has not been studied in detail. In this study, we combine the use of our whole-mount sciatic nerve staining with the use of a proteolipid protein-green fluorescent protein (PLP-GFP) mouse model to mark Schwann cells and have examined the behavior of migrating Schwann cells and regenerating axons in the sciatic nerve gap following a nerve transection injury. We show here that Schwann cell migration from both nerve stumps starts later than the regrowth of axons from the proximal nerve stump. The first migrating Schwann cells are only observed 4 days following mouse sciatic nerve transection injury. Schwann cells migrating from the proximal nerve stump overtake regenerating axons on day 5 and form Schwann cell cords within the nerve bridge by 7 days post-transection injury. Regenerating axons begin to attach to migrating Schwann cells on day 6 and then follow their trajectory navigating across the nerve gap. We also observe that Schwann cell cords in the nerve bridge are not wide enough to guide all the regenerating axons across the nerve bridge, resulting in regenerating axons growing along the outside of both proximal and distal nerve stumps. From this analysis, we demonstrate that Schwann cells play a crucial role in controlling the directionality and speed of axon regeneration across the nerve gap. We also demonstrate that the use of the PLP-GFP mouse model labeling Schwann cells together with the whole sciatic nerve axon staining technique is a useful research model to study the process of peripheral nerve regeneration.

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