1
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Warfield R, Robinson JA, Podgorski RM, Miller AD, Burdo TH. Neuroinflammation in the Dorsal Root Ganglia and Dorsal Horn Contributes to Persistence of Nociceptor Sensitization in SIV-Infected Antiretroviral Therapy-Treated Macaques. THE AMERICAN JOURNAL OF PATHOLOGY 2023; 193:2017-2030. [PMID: 37734588 PMCID: PMC10699130 DOI: 10.1016/j.ajpath.2023.08.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 07/17/2023] [Accepted: 08/16/2023] [Indexed: 09/23/2023]
Abstract
Despite the development of antiretroviral therapy (ART), HIV-associated distal sensory polyneuropathy remains prevalent. Using SIV-infected rhesus macaques, this study examined molecular mechanisms of peripheral and central sensitization to infer chronic pain from HIV infection. Previous studies identified atrophy in nociceptive neurons during SIV infection, which was associated with monocyte infiltration into the dorsal root ganglia (DRG). However, the sensory signaling mechanism connecting this pathology to symptoms remains unclear, especially because pain persists after resolution of high viremia and inflammation with ART. We hypothesized that residual DRG and dorsal horn neuroinflammation contributes to nociceptive sensitization. Using three cohorts of macaques [uninfected (SIV-), SIV-infected (SIV+), and SIV infected with ART (SIV+/ART)], this study showed an increase in the cellular and cytokine inflammatory profiles in the DRG of SIV+/ART macaques compared with uninfected animals. It found significant increase in the expression of nociceptive ion channels, TRPV1, and TRPA1 among DRG neurons in SIV+/ART compared with uninfected animals. SIV-infected and SIV+/ART animals showed reduced innervation of the nonpeptidergic nociceptors into the dorsal horn compared with uninfected animals. Finally, there were a significantly higher number of CD68+ cells in the dorsal horn of SIV+/ART macaques compared with uninfected animals. In summary, these data demonstrate that neuroinflammation, characteristics of nociceptor sensitization, and central terminal atrophy persists in SIV+/ART animals.
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Affiliation(s)
- Rebecca Warfield
- Department of Microbiology, Immunology, and Inflammation, Center for NeuroVirology and Gene Editing, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania
| | - Jake A Robinson
- Department of Microbiology, Immunology, and Inflammation, Center for NeuroVirology and Gene Editing, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania
| | - Rachel M Podgorski
- Department of Microbiology, Immunology, and Inflammation, Center for NeuroVirology and Gene Editing, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania
| | - Andrew D Miller
- Section of Anatomic Pathology, Department of Biomedical Sciences, Cornell University College of Veterinary Medicine, Ithaca, New York
| | - Tricia H Burdo
- Department of Microbiology, Immunology, and Inflammation, Center for NeuroVirology and Gene Editing, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania.
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2
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Dong X, Hong H, Cui Z. Function of GSK‑3 signaling in spinal cord injury (Review). Exp Ther Med 2023; 26:541. [PMID: 37869638 PMCID: PMC10587879 DOI: 10.3892/etm.2023.12240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 08/10/2023] [Indexed: 10/24/2023] Open
Abstract
Spinal cord injury (SCI) is a major social problem with a heavy burden on patient physiology and psychology. Glial scar formation and irreversible neuron loss are the two key points during SCI progression. During the acute phase of spinal cord injury, glial scars form, limiting the progression of inflammation. However, in the subacute or chronic phase, glial scarring inhibits axon regeneration. Following spinal cord injury, irreversible loss of neurons leads to further aggravation of spinal cord injury. Several therapies have been developed to improve either glial scar or neuron loss; however, few therapies reach the stage of clinical trials and there are no mainstream therapies for SCI. Exploring the key mechanism of SCI is crucial for finding further treatments. Glycogen synthase kinase-3 (GSK-3) is a widely expressed kinase with important physiological and pathophysiological functions in vivo. Dysfunction of the GSK-3 signaling pathway during SCI has been widely discussed for controlling neurite growth in vitro and in vivo, improving the proliferation and neuronal differentiation of endogenous neural stem cells and functional recovery from spinal cord injury. SCI can decrease the phosphorylated (p)/total (t)-GSK-3β ratio, which leads to an increase in apoptosis, whereas treatment with GSK-3 inhibitors can promote neurogenesis. In addition, several therapies for the treatment of SCI involve signaling pathways associated with GSK-3. Furthermore, signaling pathways associated with GSK-3 also participate in the pathological process of neuropathic pain that remains following SCI. The present review summarized the roles of GSK-3 signaling in SCI to aid in the understanding of GSK-3 signaling during the pathological processes of SCI and to provide evidence for the development of comprehensive treatments.
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Affiliation(s)
- Xiong Dong
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Hongxiang Hong
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Zhiming Cui
- Department of Spinal Surgery, The Second Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
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3
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Kim H, Skuba A, Xia J, Han SB, Zhai J, Hu H, Kang SH, Son YJ. Oligodendrocyte precursor cells stop sensory axons regenerating into the spinal cord. Cell Rep 2023; 42:113068. [PMID: 37656624 DOI: 10.1016/j.celrep.2023.113068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 07/17/2023] [Accepted: 08/18/2023] [Indexed: 09/03/2023] Open
Abstract
Primary somatosensory axons stop regenerating as they re-enter the spinal cord, resulting in incurable sensory loss. What arrests them has remained unclear. We previously showed that axons stop by forming synaptic contacts with unknown non-neuronal cells. Here, we identified these cells in adult mice as oligodendrocyte precursor cells (OPCs). We also found that only a few axons stop regenerating by forming dystrophic endings, exclusively at the CNS:peripheral nervous system (PNS) borderline where OPCs are absent. Most axons stop in contact with a dense network of OPC processes. Live imaging, immuno-electron microscopy (immuno-EM), and OPC-dorsal root ganglia (DRG) co-culture additionally suggest that axons are rapidly immobilized by forming synapses with OPCs. Genetic OPC ablation enables many axons to continue regenerating deep into the spinal cord. We propose that sensory axons stop regenerating by encountering OPCs that induce presynaptic differentiation. Our findings identify OPCs as a major regenerative barrier that prevents intraspinal restoration of sensory circuits following spinal root injury.
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Affiliation(s)
- Hyukmin Kim
- Department of Neural Sciences, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Andy Skuba
- Department of Neural Sciences, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Jingsheng Xia
- Department of Medicine, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - Sung Baek Han
- Department of Neural Sciences, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Jinbin Zhai
- Department of Neural Sciences, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Huijuan Hu
- Department of Medicine, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - Shin H Kang
- Department of Neural Sciences, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Young-Jin Son
- Department of Neural Sciences, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA.
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4
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Poitras T, Zochodne DW. Unleashing Intrinsic Growth Pathways in Regenerating Peripheral Neurons. Int J Mol Sci 2022; 23:13566. [PMID: 36362354 PMCID: PMC9654452 DOI: 10.3390/ijms232113566] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 10/24/2022] [Accepted: 10/28/2022] [Indexed: 10/17/2023] Open
Abstract
Common mechanisms of peripheral axon regeneration are recruited following diverse forms of damage to peripheral nerve axons. Whether the injury is traumatic or disease related neuropathy, reconnection of axons to their targets is required to restore function. Supporting peripheral axon regrowth, while not yet available in clinics, might be accomplished from several directions focusing on one or more of the complex stages of regrowth. Direct axon support, with follow on participation of supporting Schwann cells is one approach, emphasized in this review. However alternative approaches might include direct support of Schwann cells that instruct axons to regrow, manipulation of the inflammatory milieu to prevent ongoing bystander axon damage, or use of inflammatory cytokines as growth factors. Axons may be supported by a growing list of growth factors, extending well beyond the classical neurotrophin family. The understanding of growth factor roles continues to expand but their impact experimentally and in humans has faced serious limitations. The downstream signaling pathways that impact neuron growth have been exploited less frequently in regeneration models and rarely in human work, despite their promise and potency. Here we review the major regenerative signaling cascades that are known to influence adult peripheral axon regeneration. Within these pathways there are major checkpoints or roadblocks that normally check unwanted growth, but are an impediment to robust growth after injury. Several molecular roadblocks, overlapping with tumour suppressor systems in oncology, operate at the level of the perikarya. They have impacts on overall neuron plasticity and growth. A second approach targets proteins that largely operate at growth cones. Addressing both sites might offer synergistic benefits to regrowing neurons. This review emphasizes intrinsic aspects of adult peripheral axon regeneration, emphasizing several molecular barriers to regrowth that have been studied in our laboratory.
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Affiliation(s)
| | - Douglas W. Zochodne
- Neuroscience and Mental Health Institute, Division of Neurology, Department of Medicine, University of Alberta, Edmonton, AB T6G 2G3, Canada
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5
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Hausott B, Glueckert R, Schrott-Fischer A, Klimaschewski L. Signal Transduction Regulators in Axonal Regeneration. Cells 2022; 11:cells11091537. [PMID: 35563843 PMCID: PMC9104247 DOI: 10.3390/cells11091537] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 11/16/2022] Open
Abstract
Intracellular signal transduction in response to growth factor receptor activation is a fundamental process during the regeneration of the nervous system. In this context, intracellular inhibitors of neuronal growth factor signaling have become of great interest in the recent years. Among them are the prominent signal transduction regulators Sprouty (SPRY) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN), which interfere with major signaling pathways such as extracellular signal-regulated kinase (ERK) or phosphoinositide 3-kinase (PI3K)/Akt in neurons and glial cells. Furthermore, SPRY and PTEN are themselves tightly regulated by ubiquitin ligases such as c-casitas b-lineage lymphoma (c-CBL) or neural precursor cell expressed developmentally down-regulated protein 4 (NEDD4) and by different microRNAs (miRs) including miR-21 and miR-222. SPRY, PTEN and their intracellular regulators play an important role in the developing and the lesioned adult central and peripheral nervous system. This review will focus on the effects of SPRY and PTEN as well as their regulators in various experimental models of axonal regeneration in vitro and in vivo. Targeting these signal transduction regulators in the nervous system holds great promise for the treatment of neurological injuries in the future.
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Affiliation(s)
- Barbara Hausott
- Institute of Neuroanatomy, Medical University Innsbruck, 6020 Innsbruck, Austria;
- Correspondence:
| | - Rudolf Glueckert
- Department of Otorhinolaryngology, Medical University Innsbruck, 6020 Innsbruck, Austria; (R.G.); (A.S.-F.)
| | - Anneliese Schrott-Fischer
- Department of Otorhinolaryngology, Medical University Innsbruck, 6020 Innsbruck, Austria; (R.G.); (A.S.-F.)
| | - Lars Klimaschewski
- Institute of Neuroanatomy, Medical University Innsbruck, 6020 Innsbruck, Austria;
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6
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Middleton SJ, Perez-Sanchez J, Dawes JM. The structure of sensory afferent compartments in health and disease. J Anat 2021; 241:1186-1210. [PMID: 34528255 PMCID: PMC9558153 DOI: 10.1111/joa.13544] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 08/12/2021] [Accepted: 08/30/2021] [Indexed: 12/20/2022] Open
Abstract
Primary sensory neurons are a heterogeneous population of cells able to respond to both innocuous and noxious stimuli. Like most neurons they are highly compartmentalised, allowing them to detect, convey and transfer sensory information. These compartments include specialised sensory endings in the skin, the nodes of Ranvier in myelinated axons, the cell soma and their central terminals in the spinal cord. In this review, we will highlight the importance of these compartments to primary afferent function, describe how these structures are compromised following nerve damage and how this relates to neuropathic pain.
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Affiliation(s)
- Steven J Middleton
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | | | - John M Dawes
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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7
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Zhai J, Kim H, Han SB, Manire M, Yoo R, Pang S, Smith GM, Son YJ. Co-targeting myelin inhibitors and CSPGs markedly enhances regeneration of GDNF-stimulated, but not conditioning-lesioned, sensory axons into the spinal cord. eLife 2021; 10:63050. [PMID: 33942723 PMCID: PMC8139830 DOI: 10.7554/elife.63050] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 05/03/2021] [Indexed: 12/20/2022] Open
Abstract
A major barrier to intraspinal regeneration after dorsal root (DR) injury is the DR entry zone (DREZ), the CNS/PNS interface. DR axons stop regenerating at the DREZ, even if regenerative capacity is increased by a nerve conditioning lesion. This potent blockade has long been attributed to myelin-associated inhibitors and (CSPGs), but incomplete lesions and conflicting reports have prevented conclusive agreement. Here, we evaluated DR regeneration in mice using novel strategies to facilitate complete lesions and analyses, selective tracing of proprioceptive and mechanoreceptive axons, and the first simultaneous targeting of Nogo/Reticulon-4, MAG, OMgp, CSPGs, and GDNF. Co-eliminating myelin inhibitors and CSPGs elicited regeneration of only a few conditioning-lesioned DR axons across the DREZ. Their absence, however, markedly and synergistically enhanced regeneration of GDNF-stimulated axons, highlighting the importance of sufficiently elevating intrinsic growth capacity. We also conclude that myelin inhibitors and CSPGs are not the primary mechanism stopping axons at the DREZ.
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Affiliation(s)
- Jinbin Zhai
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States.,Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States
| | - Hyukmin Kim
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States.,Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States
| | - Seung Baek Han
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States.,Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States
| | - Meredith Manire
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States.,Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States
| | - Rachel Yoo
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States.,Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States
| | - Shuhuan Pang
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States.,Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States
| | - George M Smith
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States.,Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States
| | - Young-Jin Son
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States.,Center for Neural Repair and Rehabilitation, Lewis Katz School of Medicine, Temple University, Philadelphia, United States
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8
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Wu D, Jin Y, Shapiro TM, Hinduja A, Baas PW, Tom VJ. Chronic neuronal activation increases dynamic microtubules to enhance functional axon regeneration after dorsal root crush injury. Nat Commun 2020; 11:6131. [PMID: 33257677 PMCID: PMC7705672 DOI: 10.1038/s41467-020-19914-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 11/05/2020] [Indexed: 12/26/2022] Open
Abstract
After a dorsal root crush injury, centrally-projecting sensory axons fail to regenerate across the dorsal root entry zone (DREZ) to extend into the spinal cord. We find that chemogenetic activation of adult dorsal root ganglion (DRG) neurons improves axon growth on an in vitro model of the inhibitory environment after injury. Moreover, repeated bouts of daily chemogenetic activation of adult DRG neurons for 12 weeks post-crush in vivo enhances axon regeneration across a chondroitinase-digested DREZ into spinal gray matter, where the regenerating axons form functional synapses and mediate behavioral recovery in a sensorimotor task. Neuronal activation-mediated axon extension is dependent upon changes in the status of tubulin post-translational modifications indicative of highly dynamic microtubules (as opposed to stable microtubules) within the distal axon, illuminating a novel mechanism underlying stimulation-mediated axon growth. We have identified an effective combinatory strategy to promote functionally-relevant axon regeneration of adult neurons into the CNS after injury.
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Affiliation(s)
- Di Wu
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Ying Jin
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Tatiana M Shapiro
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Abhishek Hinduja
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Veronica J Tom
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, USA.
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9
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Hu X, Li R, Wu Y, Li Y, Zhong X, Zhang G, Kang Y, Liu S, Xie L, Ye J, Xiao J. Thermosensitive heparin-poloxamer hydrogel encapsulated bFGF and NGF to treat spinal cord injury. J Cell Mol Med 2020; 24:8166-8178. [PMID: 32515141 PMCID: PMC7348165 DOI: 10.1111/jcmm.15478] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 04/18/2020] [Accepted: 05/24/2020] [Indexed: 01/10/2023] Open
Abstract
The application of growth factors (GFs) for treating chronic spinal cord injury (SCI) has been shown to promote axonal regeneration and functional recovery. However, direct administration of GFs is limited by their rapid degradation and dilution at the injured sites. Moreover, SCI recovery is a multifactorial process that requires multiple GFs to participate in tissue regeneration. Based on these facts, controlled delivery of multiple growth factors (GFs) to lesion areas is becoming an attractive strategy for repairing SCI. Presently, we developed a GFs‐based delivery system (called GFs‐HP) that consisted of basic fibroblast growth factor (bFGF), nerve growth factor (NGF) and heparin‐poloxamer (HP) hydrogel through self‐assembly mode. This GFs‐HP was a kind of thermosensitive hydrogel that was suitable for orthotopic administration in vivo. Meanwhile, a 3D porous structure of this hydrogel is commonly used to load large amounts of GFs. After single injection of GFs‐HP into the lesioned spinal cord, the sustained release of NGF and bFGF from HP could significantly improve neuronal survival, axon regeneration, reactive astrogliosis suppression and locomotor recovery, when compared with the treatment of free GFs or HP. Moreover, we also revealed that these neuroprotective and neuroregenerative effects of GFs‐HP were likely through activating the phosphatidylinositol 3 kinase and protein kinase B (PI3K/Akt) and mitogen‐activated protein kinase/extracellular signal‐regulated kinase (MAPK/ERK) signalling pathways. Overall, our work will provide an effective therapeutic strategy for SCI repair.
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Affiliation(s)
- Xiaoli Hu
- Department of Anesthesia, The First Affiliated Hospital, Gannan Medical University, Ganzhou, China.,Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, China
| | - Rui Li
- Department of Anesthesia, The First Affiliated Hospital, Gannan Medical University, Ganzhou, China.,Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, China.,School of Chemistry, Sun Yat-sen University, Guangzhou, China
| | - Yanqing Wu
- The Institute of Life Sciences, Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors, Biomedical Collaborative Innovation Center of Wenzhou, Wenzhou University, Wenzhou, China
| | - Yi Li
- Department of Anesthesia, The First Affiliated Hospital, Gannan Medical University, Ganzhou, China
| | - Xingfeng Zhong
- Department of Anesthesia, Affiliated Hospital of Guizhou Medical University, Guiyang, China
| | - Guanyinsheng Zhang
- Department of Anesthesia, The First Affiliated Hospital, Gannan Medical University, Ganzhou, China
| | - Yanmin Kang
- Department of Anesthesia, The First Affiliated Hospital, Gannan Medical University, Ganzhou, China
| | - Shuhua Liu
- Department of Anesthesia, The First Affiliated Hospital, Gannan Medical University, Ganzhou, China
| | - Ling Xie
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, China
| | - Junming Ye
- Department of Anesthesia, The First Affiliated Hospital, Gannan Medical University, Ganzhou, China
| | - Jian Xiao
- Molecular Pharmacology Research Center, School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, China.,The Institute of Life Sciences, Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors, Biomedical Collaborative Innovation Center of Wenzhou, Wenzhou University, Wenzhou, China
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10
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Hausott B, Klimaschewski L. Promotion of Peripheral Nerve Regeneration by Stimulation of the Extracellular Signal-Regulated Kinase (ERK) Pathway. Anat Rec (Hoboken) 2019; 302:1261-1267. [PMID: 30951263 PMCID: PMC6767477 DOI: 10.1002/ar.24126] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 12/06/2018] [Accepted: 01/11/2019] [Indexed: 12/19/2022]
Abstract
Peripherally projecting neurons undergo significant morphological changes during development and regeneration. This neuroplasticity is controlled by growth factors, which bind specific membrane bound kinase receptors that in turn activate two major intracellular signal transduction cascades. Besides the PI3 kinase/AKT pathway, activated extracellular signal‐regulated kinase (ERK) plays a key role in regulating the mode and speed of peripheral axon outgrowth in the adult stage. Cell culture studies and animal models revealed that ERK signaling is mainly involved in elongative axon growth in vitro and long‐distance nerve regeneration in vivo. Here, we review ERK dependent morphological plasticity in adult peripheral neurons and evaluate the therapeutic potential of interfering with regulators of ERK signaling to promote nerve regeneration. Anat Rec, 302:1261–1267, 2019. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Barbara Hausott
- Department of Anatomy, Histology and Embryology, Division of Neuroanatomy, Medical University Innsbruck, Innsbruck, Austria
| | - Lars Klimaschewski
- Department of Anatomy, Histology and Embryology, Division of Neuroanatomy, Medical University Innsbruck, Innsbruck, Austria
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11
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Dubový P, Hradilová-Svíženská I, Klusáková I, Brázda V, Joukal M. Interleukin-6 contributes to initiation of neuronal regeneration program in the remote dorsal root ganglia neurons after sciatic nerve injury. Histochem Cell Biol 2019; 152:109-117. [PMID: 30927067 DOI: 10.1007/s00418-019-01779-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2019] [Indexed: 01/18/2023]
Abstract
To assess the potential role of IL-6 in sciatic nerve injury-induced activation of a pro-regenerative state in remote dorsal root ganglia (DRG) neurons, we compared protein levels of SCG-10 and activated STAT3, as well as axon regeneration in IL-6 knockout (IL-6ko) mice and their wild-type (WT) counterparts. Unilateral sciatic nerve compression and transection upregulated SCG-10 protein levels and activated STAT3 in DRG neurons not only in lumbar but also in cervical segments of WT mice. A pro-regenerative state induced by prior sciatic nerve lesion in cervical DRG neurons of WT mice was also shown by testing for axon regeneration in crushed ulnar nerve. DRG neurons from IL-6ko mice also displayed bilaterally increased levels of SCG-10 and STAT3 in both lumbar and cervical segments after sciatic nerve lesions. However, levels of SCG-10 protein in lumbar and cervical DRG of IL-6ko mice were significantly lower than those of their WT counterparts. Sciatic nerve injury induced a lower level of SCG-10 in cervical DRG of IL-6ko than WT mice, and this correlates with significantly shorter regeneration of axons distal to the crushed ulnar nerve. These results suggest that IL-6 contributes, at the very least, to initiation of the neuronal regeneration program in remote DRG neurons after unilateral sciatic nerve injury.
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Affiliation(s)
- Petr Dubový
- Department of Anatomy, Cellular and Molecular Research Group, Faculty of Medicine, Masaryk University, Kamenice 3, 62500, Brno, Czech Republic
| | - Ivana Hradilová-Svíženská
- Department of Anatomy, Cellular and Molecular Research Group, Faculty of Medicine, Masaryk University, Kamenice 3, 62500, Brno, Czech Republic
| | - Ilona Klusáková
- Department of Anatomy, Cellular and Molecular Research Group, Faculty of Medicine, Masaryk University, Kamenice 3, 62500, Brno, Czech Republic
| | - Václav Brázda
- Department of Anatomy, Cellular and Molecular Research Group, Faculty of Medicine, Masaryk University, Kamenice 3, 62500, Brno, Czech Republic
| | - Marek Joukal
- Department of Anatomy, Cellular and Molecular Research Group, Faculty of Medicine, Masaryk University, Kamenice 3, 62500, Brno, Czech Republic.
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12
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Fastigial nucleus electrostimulation promotes axonal regeneration after experimental stroke via cAMP/PKA pathway. Neurosci Lett 2019; 699:177-183. [PMID: 30753912 DOI: 10.1016/j.neulet.2019.02.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Revised: 02/04/2019] [Accepted: 02/08/2019] [Indexed: 12/13/2022]
Abstract
Axon regeneration after cerebral ischemia in mammals is inadequate to restore function, illustrating the need to design better strategies for improving outcomes. Improvement of axon regeneration has been achieved through fastigial nucleus electrostimulation (FNS) in animal researches. However, the mechanisms underlying this neuroprotection remain poorly understood. Increasing the levels of the second messenger cyclic AMP (cAMP) enhances axon regeneration, making it an excellent candidate molecule that has therapeutic potential. In the present study, we examined the expression of cAMP signaling in ischemic brain tissues following focal cerebral ischemia. Adult rats were subjected to ischemia induced by middle cerebral artery occlusion (MCAO). A dipolar electrode was placed into the cerebellum to stimulate the cerebellar fastigial nucleus for 1 h after ischemia. Neurological deficits and the expressions of cAMP, PKA (protein kinase A) and ROCK (Rho-kinase) were determined. Axonal regeneration was measured by upregulation of growth-associated protein 43 (GAP43). The data indicated that FNS significantly enhanced axonal regeneration and motor function recovery after cerebral ischemia. FNS also significantly increased cAMP and PKA levels after ischemic brain injury. All the beneficial effects of FNS were blocked by Rp-cAMP, an antagonist of PKA. Our research suggested that the axonal regeneration conferred by FNS was likely achieved via the regulation of cAMP/PKA pathway.
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Yao M, Sun H, Yuan Q, Li N, Li H, Tang Y, Leung GK, Wu W. Targeting proteoglycan receptor PTPσ restores sensory function after spinal cord dorsal root injury by activation of Erks/CREB signaling pathway. Neuropharmacology 2019; 144:208-218. [PMID: 30393073 DOI: 10.1016/j.neuropharm.2018.10.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 10/22/2018] [Accepted: 10/23/2018] [Indexed: 12/26/2022]
Abstract
Dorsal root injury commonly results in irreversible loss of sensory functions because of the limited intrinsic regenerative capacity of adult sensory axons and the growth-inhibitory environment at the dorsal root entry zone (DREZ) between the dorsal root and the spinal cord. Chondroitin sulfate proteoglycans (CSPGs) are the dominant suppressors of axonal regeneration, acting via neuronal receptors including protein tyrosine phosphatase-σ (PTPσ). ISP (Intracellular Sigma Peptide) is a small peptide mimetic of the PTPσ wedge region that has been developed to target PTPσ and relieve CSPG inhibition. Extracellular regulated kinases (Erks) and cAMP response element binding protein (CREB) are signaling molecules downstream of CSPGs and PTPσ; they are expressed in neurons and essential for axon growth. In this study, we observed that ISP administration could promote sensory function restoration in adult rats after dorsal spinal root crush injury. Our results show that systemic ISP administration would not only significantly increase sensory axon regeneration and functional recovery, but also activate Erk and CREB signaling pathway. Furthermore, ISP has also been verified to increase dorsal root ganglion axonal remyelination in vitro. These results suggest that modulation of PTPσ by ISP represents a promising therapeutic strategy for sensory neuronal injuries.
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Affiliation(s)
- Min Yao
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, 999077, China; Department of Surgery, The University of Hong Kong, Hong Kong SAR, 999077, China
| | - Haitao Sun
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, 999077, China; The National Key Clinical Specialty, The Engineering Technology Research Center of Education Ministry of China, Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China
| | - Qiuju Yuan
- School of Chinese Medicine, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, 999077, China
| | - Ning Li
- Department of Surgery, The University of Hong Kong, Hong Kong SAR, 999077, China
| | - Heng Li
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, 999077, China
| | - Yinjuan Tang
- Department of Basic Medicine Sciences, Xiangnan University, Chenzhou, 423000, Hunan Province, China
| | - Gilberto Kk Leung
- Department of Surgery, The University of Hong Kong, Hong Kong SAR, 999077, China; Guangdong-Hongkong-Macau Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, 510632, China.
| | - Wutian Wu
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, 999077, China; Guangdong-Hongkong-Macau Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, 510632, China; Re-Stem Biotechnology Co., Ltd, Suzhou, 215300, China.
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Fawcett JW, Verhaagen J. Intrinsic Determinants of Axon Regeneration. Dev Neurobiol 2018; 78:890-897. [PMID: 30345655 DOI: 10.1002/dneu.22637] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/16/2018] [Accepted: 09/16/2018] [Indexed: 12/21/2022]
Abstract
The failure of axons to regenerate in the damaged mammalian CNS is the main impediment to functional recovery. There are many molecules and structures in the environment of the injured nervous system that can inhibit regeneration, but even when these are removed or replaced with a permissive environment, most CNS neurons exhibit little regeneration of their axons. This contrasts with the extensive and vigorous axon growth that may occur when embryonic neurons are transplanted into the adult CNS. In the peripheral nervous system, the axons usually respond to axotomy with a vigorous regenerative response accompanied by a regenerative program of gene expression, usually referred to as the regeneration-associated gene (RAG) program. These different responses to axotomy in the mature and immature CNS and the PNS lead to the concept of the intrinsic regenerative response of axons. Analysis of the many mechanisms and issues that affect the intrinsic regenerative response is the topic of this special issue of Developmental Neurobiology. The review articles highlight the control of expression of growth and regeneration-associated genes, emphasizing the role of epigenetic mechanisms. The reviews also discuss changes within axons that lead to the developmental loss of regenerative ability. This is caused by changes in axonal transport and trafficking, in the cytoskeleton and in signaling pathways.
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Affiliation(s)
- James W Fawcett
- John van Geest Centre for Brain Repair, Department Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0PY, United Kingdom
| | - Joost Verhaagen
- Department of Regeneration of Sensorimotor Systems, Netherlands Institute for Neuroscience, Institute of the Royal Netherlands Academy of Arts and Sciences, Amsterdam, 1105 BA, The Netherlands
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Li R, Li Y, Wu Y, Zhao Y, Chen H, Yuan Y, Xu K, Zhang H, Lu Y, Wang J, Li X, Jia X, Xiao J. Heparin-Poloxamer Thermosensitive Hydrogel Loaded with bFGF and NGF Enhances Peripheral Nerve Regeneration in Diabetic Rats. Biomaterials 2018; 168:24-37. [PMID: 29609091 PMCID: PMC5935004 DOI: 10.1016/j.biomaterials.2018.03.044] [Citation(s) in RCA: 149] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 03/21/2018] [Accepted: 03/24/2018] [Indexed: 12/13/2022]
Abstract
Peripheral nerve injury (PNI) is a major burden to society with limited therapeutic options, and novel biomaterials have great potential for shifting the current paradigm of treatment. With a rising prevalence of chronic illnesses such as diabetes mellitus (DM), treatment of PNI is further complicated, and only few studies have proposed therapies suitable for peripheral nerve regeneration in DM. To provide a supportive environment to restore structure and/or function of nerves in DM, we developed a novel thermo-sensitive heparin-poloxamer (HP) hydrogel co-delivered with basic fibroblast growth factor (bFGF) and nerve growth factor (NGF) in diabetic rats with sciatic nerve crush injury. The delivery vehicle not only had a good affinity for large amounts of growth factors (GFs), but also controlled their release in a steady fashion, preventing degradation in vitro. In vivo, compared with HP hydrogel alone or direct GFs administration, GFs-HP hydrogel treatment is more effective at facilitating Schwann cell (SC) proliferation, leading to an increased expression of nerve associated structural proteins, enhanced axonal regeneration and remyelination, and improved recovery of motor function (all p < 0.05). Our mechanistic investigation also revealed that these neuroprotective and neuroregenerative effects of the GFs-HP hydrogel may be associated with activations of phosphatidylinositol 3 kinase and protein kinase B (PI3K/Akt), janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3), and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling pathways. Our work provides a promising therapy option for peripheral nerve regeneration in patients with DM.
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Affiliation(s)
- Rui Li
- Molecular Pharmacology Research Center, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Yiyang Li
- Molecular Pharmacology Research Center, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Yanqing Wu
- The Institute of Life Sciences, Wenzhou University, Wenzhou 325035, China
| | - Yingzheng Zhao
- Molecular Pharmacology Research Center, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Huanwen Chen
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Yuan Yuan
- Molecular Pharmacology Research Center, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Ke Xu
- The Institute of Life Sciences, Wenzhou University, Wenzhou 325035, China
| | - Hongyu Zhang
- Molecular Pharmacology Research Center, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China
| | - Yingfeng Lu
- Department of Peripheral Neurosurgery, The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, 325000, China
| | - Jian Wang
- Department of Peripheral Neurosurgery, The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, 325000, China
| | - Xiaokun Li
- The Institute of Life Sciences, Wenzhou University, Wenzhou 325035, China
| | - Xiaofeng Jia
- Department of Neurosurgery, Orthopaedics, Anatomy Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Biomedical Engineering, Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Jian Xiao
- Molecular Pharmacology Research Center, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China.
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Murillo B, Mendes Sousa M. Neuronal Intrinsic Regenerative Capacity: The Impact of Microtubule Organization and Axonal Transport. Dev Neurobiol 2018; 78:952-959. [PMID: 29738096 DOI: 10.1002/dneu.22602] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 04/20/2018] [Accepted: 04/25/2018] [Indexed: 11/06/2022]
Abstract
In the adult vertebrate central nervous system, axons generally fail to regenerate. In contrast, peripheral nervous system axons are able to form a growth cone and regenerate upon lesion. Among the multiple intrinsic mechanisms leading to the formation of a new growth cone and to successful axon regrowth, cytoskeleton organization and dynamics is central. Here we discuss how multiple pathways that define the regenerative capacity converge into the regulation of the axonal microtubule cytoskeleton and transport. We further explore the use of dorsal root ganglion neurons as a model to study the neuronal regenerative ability. Finally, we address some of the unanswered questions in the field, including the mechanisms by which axonal transport might be modulated by injury, and the relationship between microtubule organization, dynamics, and axonal transport. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 00: 000-000, 2018.
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Affiliation(s)
- Blanca Murillo
- Nerve Regeneration group, Instituto de Biologia Molecular e Celular - IBMC and Instituto de Inovação e Investigação em Saúde, University of Porto, Rua Alfredo Allen 208, Porto, 4200-135, Portugal
| | - Mónica Mendes Sousa
- Nerve Regeneration group, Instituto de Biologia Molecular e Celular - IBMC and Instituto de Inovação e Investigação em Saúde, University of Porto, Rua Alfredo Allen 208, Porto, 4200-135, Portugal
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Nascimento AI, Mar FM, Sousa MM. The intriguing nature of dorsal root ganglion neurons: Linking structure with polarity and function. Prog Neurobiol 2018; 168:86-103. [PMID: 29729299 DOI: 10.1016/j.pneurobio.2018.05.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 04/26/2018] [Accepted: 05/01/2018] [Indexed: 11/26/2022]
Abstract
Dorsal root ganglion (DRG) neurons are the first neurons of the sensory pathway. They are activated by a variety of sensory stimuli that are then transmitted to the central nervous system. An important feature of DRG neurons is their unique morphology where a single process -the stem axon- bifurcates into a peripheral and a central axonal branch, with different functions and cellular properties. Distinctive structural aspects of the two DRG neuron branches may have important implications for their function in health and disease. However, the link between DRG axonal branch structure, polarity and function has been largely neglected in the field, and relevant information is rather scattered across the literature. In particular, ultrastructural differences between the two axonal branches are likely to account for the higher transport and regenerative ability of the peripheral DRG neuron axon when compared to the central one. Nevertheless, the cell intrinsic factors contributing to this central-peripheral asymmetry are still unknown. Here we critically review the factors that may underlie the functional asymmetry between the peripheral and central DRG axonal branches. Also, we discuss the hypothesis that DRG neurons may assemble a structure resembling the axon initial segment that may be responsible, at least in part, for their polarity and electrophysiological features. Ultimately, we suggest that the clarification of the axonal ultrastructure of DRG neurons using state-of-the-art techniques will be crucial to understand the physiology of this peculiar cell type.
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Affiliation(s)
- Ana Isabel Nascimento
- Nerve Regeneration Group, Instituto de Biologia Molecular e Celular-IBMC and Instituto de Inovação e Investigação em Saúde, University of Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal; Instituto de Ciências Biomédicas Abel Salazar-ICBAS, Rua Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Fernando Milhazes Mar
- Nerve Regeneration Group, Instituto de Biologia Molecular e Celular-IBMC and Instituto de Inovação e Investigação em Saúde, University of Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal
| | - Mónica Mendes Sousa
- Nerve Regeneration Group, Instituto de Biologia Molecular e Celular-IBMC and Instituto de Inovação e Investigação em Saúde, University of Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal.
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18
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Yuan Q, Sun L, Yu H, An C. Human microvascular endothelial cell promotes the development of dorsal root ganglion neurons via BDNF pathway in a co-culture system. Biosci Biotechnol Biochem 2017; 81:1335-1342. [PMID: 28394221 DOI: 10.1080/09168451.2017.1313695] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Our previous study found that co-culture with human vascular endothelial cells (HMVECs) is beneficial for dorsal root ganglion cells (DRGCs). The goal of the present study is to investigate whether co-culture with HMVECs could promote the development of DRGCs, and whether this effect is induced by the secretion of BDNF by HMVECs. DRGCs were mono-cultured, co-cultured with HMVECs or co-cultured with HMVECs that pre-transfected with BDNF siRNA, the expression of neurite formation and branching factors were determined. The results showed that transfecting with BDNF siRNA inhibited BDNF expression and reduced BDNF secretion. Co-culture with HMVECs increased the expression of Etv4, Etv5, FN-L, FN-M, and GAP-43 in DRGCs that accompanied by the activation of ERK pathway. However, these changes were all reversed by the inhibition of BDNF in HMVECs. In conclusion, our data demonstrate that HMVECs potentiated DRGCs development at least partly by the secretion of BDNF in the co-culture system.
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Affiliation(s)
- Quan Yuan
- a Department of Orthopedics , Shengjing Hospital of China Medical University , Shenyang , People's Republic of China
| | - Li Sun
- b Department of Nephrology , The First Affiliated Hospital of China Medical University , Shenyang , People's Republic of China
| | - Honghao Yu
- a Department of Orthopedics , Shengjing Hospital of China Medical University , Shenyang , People's Republic of China
| | - Chunhou An
- a Department of Orthopedics , Shengjing Hospital of China Medical University , Shenyang , People's Republic of China
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19
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Zhong J. RAS and downstream RAF-MEK and PI3K-AKT signaling in neuronal development, function and dysfunction. Biol Chem 2016; 397:215-22. [PMID: 26760308 DOI: 10.1515/hsz-2015-0270] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 01/04/2016] [Indexed: 12/12/2022]
Abstract
In postmitotic neurons, the activation of RAS family small GTPases regulates survival, growth and differentiation. Dysregulation of RAS or its major effector pathway, the cascade of RAF-, mitogen-activated and extracellular-signal regulated kinase kinases (MEK), and extracellular-signal regulated kinases (ERK) causes the RASopathies, a group of neurodevelopmental disorders whose pathogenic mechanisms are the subject of intense research. I here summarize the functions of RAS-RAF-MEK-ERK signaling in neurons in vivo, and discuss perspectives for harnessing this pathway to enable novel treatments for nervous system injury, the RASopathies, and possibly other neurological conditions.
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20
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Wu D, Klaw MC, Kholodilov N, Burke RE, Detloff MR, Côté MP, Tom VJ. Expressing Constitutively Active Rheb in Adult Dorsal Root Ganglion Neurons Enhances the Integration of Sensory Axons that Regenerate Across a Chondroitinase-Treated Dorsal Root Entry Zone Following Dorsal Root Crush. Front Mol Neurosci 2016; 9:49. [PMID: 27458339 PMCID: PMC4932115 DOI: 10.3389/fnmol.2016.00049] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 06/07/2016] [Indexed: 11/13/2022] Open
Abstract
While the peripheral branch of dorsal root ganglion neurons (DRG) can successfully regenerate after injury, lesioned central branch axons fail to regrow across the dorsal root entry zone (DREZ), the interface between the dorsal root and the spinal cord. This lack of regeneration is due to the limited regenerative capacity of adult sensory axons and the growth-inhibitory environment at the DREZ, which is similar to that found in the glial scar after a central nervous system (CNS) injury. We hypothesized that transduction of adult DRG neurons using adeno-associated virus (AAV) to express a constitutively-active form of the GTPase Rheb (caRheb) will increase their intrinsic growth potential after a dorsal root crush. Additionally, we posited that if we combined that approach with digestion of upregulated chondroitin sulfate proteoglycans (CSPG) at the DREZ with chondroitinase ABC (ChABC), we would promote regeneration of sensory axons across the DREZ into the spinal cord. We first assessed if this strategy promotes neuritic growth in an in vitro model of the glial scar containing CSPG. ChABC allowed for some regeneration across the once potently inhibitory substrate. Combining ChABC treatment with expression of caRheb in DRG significantly improved this growth. We then determined if this combination strategy also enhanced regeneration through the DREZ after dorsal root crush in adult rats in vivo. After unilaterally crushing C4-T1 dorsal roots, we injected AAV5-caRheb or AAV5-GFP into the ipsilateral C5-C8 DRGs. ChABC or PBS was injected into the ipsilateral dorsal horn at C5-C8 to digest CSPG, for a total of four animal groups (caRheb + ChABC, caRheb + PBS, GFP + ChABC, GFP + PBS). Regeneration was rarely observed in PBS-treated animals, whereas short-distance regrowth across the DREZ was observed in ChABC-treated animals. No difference in axon number or length between the ChABC groups was observed, which may be related to intraganglionic inflammation induced by the injection. ChABC-mediated regeneration is functional, as stimulation of ipsilateral median and ulnar nerves induced neuronal c-Fos expression in deafferented dorsal horn in both ChABC groups. Interestingly, caRheb + ChABC animals had significantly more c-Fos+ nuclei indicating that caRheb expression in DRGs promoted functional synaptogenesis of their axons that regenerated beyond a ChABC-treated DREZ.
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Affiliation(s)
- Di Wu
- Department of Neurobiology and Anatomy, Drexel University College of Medicine Philadelphia, PA, USA
| | - Michelle C Klaw
- Department of Neurobiology and Anatomy, Drexel University College of Medicine Philadelphia, PA, USA
| | - Nikolai Kholodilov
- Department of Neurology, Columbia University in the City of New York New York, NY, USA
| | - Robert E Burke
- Department of Neurology, Columbia University in the City of New YorkNew York, NY, USA; Department of Pathology and Cell Biology, Columbia University in the City of New YorkNew York, NY, USA
| | - Megan R Detloff
- Department of Neurobiology and Anatomy, Drexel University College of Medicine Philadelphia, PA, USA
| | - Marie-Pascale Côté
- Department of Neurobiology and Anatomy, Drexel University College of Medicine Philadelphia, PA, USA
| | - Veronica J Tom
- Department of Neurobiology and Anatomy, Drexel University College of Medicine Philadelphia, PA, USA
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