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Gordon T. Physiology of Nerve Regeneration: Key Factors Affecting Clinical Outcomes. Hand Clin 2024; 40:337-345. [PMID: 38972678 DOI: 10.1016/j.hcl.2024.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/09/2024]
Abstract
Functional recovery after peripheral nerve injuries is disappointing despite surgical advances in nerve repair. This review summarizes the relatively short window of opportunity for successful nerve regeneration due to the decline in the expression of growth-associated genes and in turn, the decline in regenerative capacity of the injured neurons and the support provided by the denervated Schwann cells, and the atrophy of denervated muscles. Brief, low-frequency electrical stimulation and post-injury exercise regimes ameliorate these deficits in animal models and patients, but the misdirection of regenerating nerve fibers compromises functional recovery and remains an important area of future research.
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Affiliation(s)
- Tessa Gordon
- Department of Surgery, University of Toronto, Toronto, Ontario M5G 1X8, Canada.
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2
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Sahoo PK, Hanovice N, Ward P, Agrawal M, Smith TP, SiMa H, Dulin JN, Vaughn LS, Tuszynski M, Welshhans K, Benowitz L, English A, Houle JD, Twiss JL. Disruption of Core Stress Granule Protein Aggregates Promotes CNS Axon Regeneration. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.07.597743. [PMID: 38895344 PMCID: PMC11185597 DOI: 10.1101/2024.06.07.597743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Depletion or inhibition of core stress granule proteins, G3BP1 in mammals and TIAR-2 in C. elegans , increases axon regeneration in injured neurons that show spontaneous regeneration. Inhibition of G3BP1 by expression of its acidic or 'B-domain' accelerates axon regeneration after nerve injury bringing a potential therapeutic intervention to promote neural repair in the peripheral nervous system. Here, we asked if G3BP1 inhibition is a viable strategy to promote regeneration in the injured mammalian central nervous system where axons do not regenerate spontaneously. G3BP1 B-domain expression was found to promote axon regeneration in both the mammalian spinal cord and optic nerve. Moreover, a cell permeable peptide to a subregion of G3BP1's B-domain (rodent G3BP1 amino acids 190-208) accelerated axon regeneration after peripheral nerve injury and promoted the regrowth of reticulospinal axons into the distal transected spinal cord through a bridging peripheral nerve graft. The rodent and human G3BP1 peptides promoted axon growth from rodent and human neurons cultured on permissive substrates, and this function required alternating Glu/Asp-Pro repeats that impart a unique predicted tertiary structure. These studies point to G3BP1 granules as a critical impediment to CNS axon regeneration and indicate that G3BP1 granule disassembly represents a novel therapeutic strategy for promoting neural repair after CNS injury.
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Hingorani S, Paniagua Soriano G, Sánchez Huertas C, Villalba Riquelme EM, López Mocholi E, Martínez Rojas B, Alastrué Agudo A, Dupraz S, Ferrer Montiel AV, Moreno Manzano V. Transplantation of dorsal root ganglia overexpressing the NaChBac sodium channel improves locomotion after complete SCI. Mol Ther 2024; 32:1739-1759. [PMID: 38556794 PMCID: PMC11184342 DOI: 10.1016/j.ymthe.2024.03.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 02/21/2024] [Accepted: 03/28/2024] [Indexed: 04/02/2024] Open
Abstract
Spinal cord injury (SCI) is a debilitating condition currently lacking treatment. Severe SCI causes the loss of most supraspinal inputs and neuronal activity caudal to the injury, which, coupled with the limited endogenous capacity for spontaneous regeneration, can lead to complete functional loss even in anatomically incomplete lesions. We hypothesized that transplantation of mature dorsal root ganglia (DRGs) genetically modified to express the NaChBac sodium channel could serve as a therapeutic option for functionally complete SCI. We found that NaChBac expression increased the intrinsic excitability of DRG neurons and promoted cell survival and neurotrophic factor secretion in vitro. Transplantation of NaChBac-expressing dissociated DRGs improved voluntary locomotion 7 weeks after injury compared to control groups. Animals transplanted with NaChBac-expressing DRGs also possessed higher tubulin-positive neuronal fiber and myelin preservation, although serotonergic descending fibers remained unaffected. We observed early preservation of the corticospinal tract 14 days after injury and transplantation, which was lost 7 weeks after injury. Nevertheless, transplantation of NaChBac-expressing DRGs increased the neuronal excitatory input by an increased number of VGLUT2 contacts immediately caudal to the injury. Our work suggests that the transplantation of NaChBac-expressing dissociated DRGs can rescue significant motor function, retaining an excitatory neuronal relay activity immediately caudal to injury.
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Affiliation(s)
- Sonia Hingorani
- Neuronal and Tissue Regeneration Laboratory, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
| | - Guillem Paniagua Soriano
- Neuronal and Tissue Regeneration Laboratory, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
| | - Carlos Sánchez Huertas
- Development and Assembly of Bilateral Neural Circuits Laboratory, Instituto de Neurociencias, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Miguel Hernández, Avenida Santiago Ramon y Cajal, s/n, 03550 Sant Joan d'Alacant, Alicante, Spain
| | - Eva María Villalba Riquelme
- Biochemistry and Molecular Biology Department, Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche-IDiBE, Avenida de la Universidad, s/n, Edificio Torregaitán, 03202 Elche, Alicante, Spain
| | - Eric López Mocholi
- Neuronal and Tissue Regeneration Laboratory, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
| | - Beatriz Martínez Rojas
- Neuronal and Tissue Regeneration Laboratory, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
| | - Ana Alastrué Agudo
- Neuronal and Tissue Regeneration Laboratory, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
| | - Sebastián Dupraz
- Laboratory for Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
| | - Antonio Vicente Ferrer Montiel
- Biochemistry and Molecular Biology Department, Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche-IDiBE, Avenida de la Universidad, s/n, Edificio Torregaitán, 03202 Elche, Alicante, Spain
| | - Victoria Moreno Manzano
- Neuronal and Tissue Regeneration Laboratory, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain.
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Jerome AD, Sas AR, Wang Y, Hammond LA, Wen J, Atkinson JR, Webb A, Liu T, Segal BM. Cytokine polarized, alternatively activated bone marrow neutrophils drive axon regeneration. Nat Immunol 2024; 25:957-968. [PMID: 38811815 DOI: 10.1038/s41590-024-01836-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 04/11/2024] [Indexed: 05/31/2024]
Abstract
The adult central nervous system (CNS) possesses a limited capacity for self-repair. Severed CNS axons typically fail to regrow. There is an unmet need for treatments designed to enhance neuronal viability, facilitate axon regeneration and ultimately restore lost neurological functions to individuals affected by traumatic CNS injury, multiple sclerosis, stroke and other neurological disorders. Here we demonstrate that both mouse and human bone marrow neutrophils, when polarized with a combination of recombinant interleukin-4 (IL-4) and granulocyte colony-stimulating factor (G-CSF), upregulate alternative activation markers and produce an array of growth factors, thereby gaining the capacity to promote neurite outgrowth. Moreover, adoptive transfer of IL-4/G-CSF-polarized bone marrow neutrophils into experimental models of CNS injury triggered substantial axon regeneration within the optic nerve and spinal cord. These findings have far-reaching implications for the future development of autologous myeloid cell-based therapies that may bring us closer to effective solutions for reversing CNS damage.
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Affiliation(s)
- Andrew D Jerome
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- The Neuroscience Research Institute, The Ohio State University, Columbus, OH, USA
| | - Andrew R Sas
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- The Neuroscience Research Institute, The Ohio State University, Columbus, OH, USA
| | - Yan Wang
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- The Neuroscience Research Institute, The Ohio State University, Columbus, OH, USA
| | - Luke A Hammond
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- The Neuroscience Research Institute, The Ohio State University, Columbus, OH, USA
| | - Jing Wen
- The James Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA
| | - Jeffrey R Atkinson
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Amy Webb
- The James Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA
- Department of Biomedical Informatics, The Ohio State University, Columbus, OH, USA
| | - Tom Liu
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- The Neuroscience Research Institute, The Ohio State University, Columbus, OH, USA
| | - Benjamin M Segal
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA.
- The Neuroscience Research Institute, The Ohio State University, Columbus, OH, USA.
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Talsma AD, Niemi JP, Zigmond RE. Neither injury induced macrophages within the nerve, nor the environment created by Wallerian degeneration is necessary for enhanced in vivo axon regeneration after peripheral nerve injury. J Neuroinflammation 2024; 21:134. [PMID: 38802868 PMCID: PMC11131297 DOI: 10.1186/s12974-024-03132-5] [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: 04/23/2024] [Accepted: 05/13/2024] [Indexed: 05/29/2024] Open
Abstract
BACKGROUND Since the 1990s, evidence has accumulated that macrophages promote peripheral nerve regeneration and are required for enhancing regeneration in the conditioning lesion (CL) response. After a sciatic nerve injury, macrophages accumulate in the injury site, the nerve distal to that site, and the axotomized dorsal root ganglia (DRGs). In the peripheral nervous system, as in other tissues, the macrophage response is derived from both resident macrophages and recruited monocyte-derived macrophages (MDMs). Unresolved questions are: at which sites do macrophages enhance nerve regeneration, and is a particular population needed. METHODS Ccr2 knock-out (KO) and Ccr2gfp/gfp knock-in/KO mice were used to prevent MDM recruitment. Using these strains in a sciatic CL paradigm, we examined the necessity of MDMs and residents for CL-enhanced regeneration in vivo and characterized injury-induced nerve inflammation. CL paradigm variants, including the addition of pharmacological macrophage depletion methods, tested the role of various macrophage populations in initiating or sustaining the CL response. In vivo regeneration, measured from bilateral proximal test lesions (TLs) after 2 d, and macrophages were quantified by immunofluorescent staining. RESULTS Peripheral CL-enhanced regeneration was equivalent between crush and transection CLs and was sustained for 28 days in both Ccr2 KO and WT mice despite MDM depletion. Similarly, the central CL response measured in dorsal roots was unchanged in Ccr2 KO mice. Macrophages at both the TL and CL, but not between them, stained for the pro-regenerative marker, arginase 1. TL macrophages were primarily CCR2-dependent MDMs and nearly absent in Ccr2 KO and Ccr2gfp/gfp KO mice. However, there were only slightly fewer Arg1+ macrophages in CCR2 null CLs than controls due to resident macrophage compensation. Zymosan injection into an intact WT sciatic nerve recruited Arg1+ macrophages but did not enhance regeneration. Finally, clodronate injection into Ccr2gfp KO CLs dramatically reduced CL macrophages. Combined with the Ccr2gfp KO background, depleting MDMs and TL macrophages, and a transection CL, physically removing the distal nerve environment, nearly all macrophages in the nerve were removed, yet CL-enhanced regeneration was not impaired. CONCLUSIONS Macrophages in the sciatic nerve are neither necessary nor sufficient to produce a CL response.
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Affiliation(s)
- Aaron D Talsma
- Department of Neurosciences, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106-4975, USA
| | - Jon P Niemi
- Department of Neurosciences, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106-4975, USA
| | - Richard E Zigmond
- Department of Neurosciences, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106-4975, USA.
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Kvistad CE, Kråkenes T, Gavasso S, Bø L. Neural regeneration in the human central nervous system-from understanding the underlying mechanisms to developing treatments. Where do we stand today? Front Neurol 2024; 15:1398089. [PMID: 38803647 PMCID: PMC11129638 DOI: 10.3389/fneur.2024.1398089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 04/22/2024] [Indexed: 05/29/2024] Open
Abstract
Mature neurons in the human central nervous system (CNS) fail to regenerate after injuries. This is a common denominator across different aetiologies, including multiple sclerosis, spinal cord injury and ischemic stroke. The lack of regeneration leads to permanent functional deficits with a substantial impact on patient quality of life, representing a significant socioeconomic burden worldwide. Great efforts have been made to decipher the responsible mechanisms and we now know that potent intra- and extracellular barriers prevent axonal repair. This knowledge has resulted in numerous clinical trials, aiming to promote neuroregeneration through different approaches. Here, we summarize the current understanding of the causes to the poor regeneration within the human CNS. We also review the results of the treatment attempts that have been translated into clinical trials so far.
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Affiliation(s)
| | - Torbjørn Kråkenes
- Neuro-SysMed, Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | - Sonia Gavasso
- Neuro-SysMed, Department of Neurology, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Lars Bø
- Neuro-SysMed, Department of Neurology, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
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Gordon T. Brief Electrical Stimulation Promotes Recovery after Surgical Repair of Injured Peripheral Nerves. Int J Mol Sci 2024; 25:665. [PMID: 38203836 PMCID: PMC10779324 DOI: 10.3390/ijms25010665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 12/07/2023] [Accepted: 12/08/2023] [Indexed: 01/12/2024] Open
Abstract
Injured peripheral nerves regenerate their axons in contrast to those in the central nervous system. Yet, functional recovery after surgical repair is often disappointing. The basis for poor recovery is progressive deterioration with time and distance of the growth capacity of the neurons that lose their contact with targets (chronic axotomy) and the growth support of the chronically denervated Schwann cells (SC) in the distal nerve stumps. Nonetheless, chronically denervated atrophic muscle retains the capacity for reinnervation. Declining electrical activity of motoneurons accompanies the progressive fall in axotomized neuronal and denervated SC expression of regeneration-associated-genes and declining regenerative success. Reduced motoneuronal activity is due to the withdrawal of synaptic contacts from the soma. Exogenous neurotrophic factors that promote nerve regeneration can replace the endogenous factors whose expression declines with time. But the profuse axonal outgrowth they provoke and the difficulties in their delivery hinder their efficacy. Brief (1 h) low-frequency (20 Hz) electrical stimulation (ES) proximal to the injury site promotes the expression of endogenous growth factors and, in turn, dramatically accelerates axon outgrowth and target reinnervation. The latter ES effect has been demonstrated in both rats and humans. A conditioning ES of intact nerve days prior to nerve injury increases axonal outgrowth and regeneration rate. Thereby, this form of ES is amenable for nerve transfer surgeries and end-to-side neurorrhaphies. However, additional surgery for applying the required electrodes may be a hurdle. ES is applicable in all surgeries with excellent outcomes.
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Affiliation(s)
- Tessa Gordon
- Division of Reconstructive Surgery, Department of Surgery, University of Toronto, Toronto, ON M4G 1X8, Canada
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8
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Zhao Q, Jiang C, Zhao L, Dai X, Yi S. Unleashing Axonal Regeneration Capacities: Neuronal and Non-neuronal Changes After Injuries to Dorsal Root Ganglion Neuron Central and Peripheral Axonal Branches. Mol Neurobiol 2024; 61:423-433. [PMID: 37620687 DOI: 10.1007/s12035-023-03590-7] [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: 02/23/2023] [Accepted: 08/16/2023] [Indexed: 08/26/2023]
Abstract
Peripheral nerves obtain remarkable regenerative capacity while central nerves can hardly regenerate following nerve injury. Sensory neurons in the dorsal root ganglion (DRG) are widely used to decipher the dissimilarity between central and peripheral axonal regeneration as axons of DRG neurons bifurcate into the regeneration-incompetent central projections and the regeneration-competent peripheral projections. A conditioning peripheral branch injury facilitates central axonal regeneration and enables the growth and elongation of central axons. Peripheral axonal injury stimulates neuronal calcium influx, alters the start-point chromatin states, increases chromatin accessibility, upregulates the expressions of regeneration-promoting genes and the synthesis of proteins, and supports axonal regeneration. Following central axonal injury, the responses of DRG neurons are modest, resulting in poor intrinsic growth ability. Some non-neuronal cells in DRGs, for instance satellite glial cells, also exhibit diminished injury responses to central axon injury as compared with peripheral axon injury. Moreover, DRG central and peripheral axonal branches are respectively surrounded by inhibitory glial scars generated by central glial cells and a permissive microenvironment generated by Schwann cells and macrophages. The aim of this review is to look at changes of DRG neurons and non-neuronal cells after peripheral and central axon injuries and summarize the contributing roles of both neuronal intrinsic regenerative capacities and surrounding microenvironments in axonal regeneration.
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Affiliation(s)
- Qian Zhao
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-Innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu, China
| | - Chunyi Jiang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-Innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu, China
- Department of Pathology, Nantong University Affiliated Hospital, Nantong, Jiangsu, China
| | - Li Zhao
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-Innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu, China
| | - Xiu Dai
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-Innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu, China.
| | - Sheng Yi
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-Innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu, China.
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Yu D, Zeng X, Aljuboori ZS, Dennison R, Wu L, Anderson JA, Teng YD. T12-L3 Nerve Transfer-Induced Locomotor Recovery in Rats with Thoracolumbar Contusion: Essential Roles of Sensory Input Rerouting and Central Neuroplasticity. Cells 2023; 12:2804. [PMID: 38132124 PMCID: PMC10741684 DOI: 10.3390/cells12242804] [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: 10/09/2023] [Revised: 11/28/2023] [Accepted: 12/05/2023] [Indexed: 12/23/2023] Open
Abstract
Locomotor recovery after spinal cord injury (SCI) remains an unmet challenge. Nerve transfer (NT), the connection of a functional/expendable peripheral nerve to a paralyzed nerve root, has long been clinically applied, aiming to restore motor control. However, outcomes have been inconsistent, suggesting that NT-induced neurological reinstatement may require activation of mechanisms beyond motor axon reinnervation (our hypothesis). We previously reported that to enhance rat locomotion following T13-L1 hemisection, T12-L3 NT must be performed within timeframes optimal for sensory nerve regrowth. Here, T12-L3 NT was performed for adult female rats with subacute (7-9 days) or chronic (8 weeks) mild (SCImi: 10 g × 12.5 mm) or moderate (SCImo: 10 g × 25 mm) T13-L1 thoracolumbar contusion. For chronic injuries, T11-12 implantation of adult hMSCs (1-week before NT), post-NT intramuscular delivery of FGF2, and environmentally enriched/enlarged (EEE) housing were provided. NT, not control procedures, qualitatively improved locomotion in both SCImi groups and animals with subacute SCImo. However, delayed NT did not produce neurological scale upgrading conversion for SCImo rats. Ablation of the T12 ventral/motor or dorsal/sensory root determined that the T12-L3 sensory input played a key role in hindlimb reanimation. Pharmacological, electrophysiological, and trans-synaptic tracing assays revealed that NT strengthened integrity of the propriospinal network, serotonergic neuromodulation, and the neuromuscular junction. Besides key outcomes of thoracolumbar contusion modeling, the data provides the first evidence that mixed NT-induced locomotor efficacy may rely pivotally on sensory rerouting and pro-repair neuroplasticity to reactivate neurocircuits/central pattern generators. The finding describes a novel neurobiology mechanism underlying NT, which can be targeted for development of innovative neurotization therapies.
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Affiliation(s)
- Dou Yu
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Xiang Zeng
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Zaid S. Aljuboori
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Rachel Dennison
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Liquan Wu
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Jamie A. Anderson
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Yang D. Teng
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
- Neurotrauma Recovery Research, Spaulding Rehabilitation Hospital Network, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
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Wang Y, Halawani D, Estill M, Ramakrishnan A, Shen L, Friedel RH, Zou H. Aryl hydrocarbon receptor restricts axon regeneration of DRG neurons in response to injury. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.04.565649. [PMID: 37961567 PMCID: PMC10635160 DOI: 10.1101/2023.11.04.565649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Injured neurons sense environmental cues to balance neural protection and axon regeneration, but the mechanisms are unclear. Here, we unveil aryl hydrocarbon receptor (AhR), a ligand-activated bHLH-PAS transcription factor, as molecular sensor and key regulator of acute stress response at the expense of axon regeneration. We demonstrate responsiveness of DRG sensory neurons to ligand-mediated AhR signaling, which functions to inhibit axon regeneration. Ahr deletion mimics the conditioning lesion in priming DRG to initiate axonogenesis gene programs; upon peripheral axotomy, Ahr ablation suppresses inflammation and stress signaling while augmenting pro-growth pathways. Moreover, comparative transcriptomics revealed signaling interactions between AhR and HIF-1α, two structurally related bHLH-PAS α units that share the dimerization partner Arnt/HIF-1β. Functional assays showed that the growth advantage of AhR-deficient DRG neurons requires HIF-1α; but in the absence of Arnt, DRG neurons can still mount a regenerative response. We further unveil a link between bHLH-PAS transcription factors and DNA hydroxymethylation in response to peripheral axotomy, while neuronal single cell RNA-seq analysis revealed a link of the AhR regulon to RNA polymerase III regulation and integrated stress response (ISR). Altogether, AhR activation favors stress coping and inflammation at the expense of axon regeneration; targeting AhR can enhance nerve repair.
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Affiliation(s)
- Yiqun Wang
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, USA
- Current address: Sport Medicine Center, Honghui Hospital, Xi’an Jiaotong University, Xi’an, China
| | - Dalia Halawani
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, USA
| | - Molly Estill
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, USA
| | - Aarthi Ramakrishnan
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, USA
| | - Li Shen
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, USA
| | - Roland H. Friedel
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, USA
- Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, USA
| | - Hongyan Zou
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, USA
- Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, USA
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11
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Benowitz LI, Xie L, Yin Y. Inflammatory Mediators of Axon Regeneration in the Central and Peripheral Nervous Systems. Int J Mol Sci 2023; 24:15359. [PMID: 37895039 PMCID: PMC10607492 DOI: 10.3390/ijms242015359] [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: 08/31/2023] [Revised: 10/13/2023] [Accepted: 10/13/2023] [Indexed: 10/29/2023] Open
Abstract
Although most pathways in the mature central nervous system cannot regenerate when injured, research beginning in the late 20th century has led to discoveries that may help reverse this situation. Here, we highlight research in recent years from our laboratory identifying oncomodulin (Ocm), stromal cell-derived factor (SDF)-1, and chemokine CCL5 as growth factors expressed by cells of the innate immune system that promote axon regeneration in the injured optic nerve and elsewhere in the central and peripheral nervous systems. We also review the role of ArmC10, a newly discovered Ocm receptor, in mediating many of these effects, and the synergy between inflammation-derived growth factors and complementary strategies to promote regeneration, including deleting genes encoding cell-intrinsic suppressors of axon growth, manipulating transcription factors that suppress or promote the expression of growth-related genes, and manipulating cell-extrinsic suppressors of axon growth. In some cases, combinatorial strategies have led to unprecedented levels of nerve regeneration. The identification of some similar mechanisms in human neurons offers hope that key discoveries made in animal models may eventually lead to treatments to improve outcomes after neurological damage in patients.
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Affiliation(s)
- Larry I. Benowitz
- Department of Neurosurgery, Boston Children’s Hospital, Boston, MA 02115, USA; (L.X.); (Y.Y.)
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA 02115, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA
- Department of Ophthalmology, University of Pittsburgh Medical Center, Pittsburgh, PA 15213, USA
| | - Lili Xie
- Department of Neurosurgery, Boston Children’s Hospital, Boston, MA 02115, USA; (L.X.); (Y.Y.)
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Department of Ophthalmology, Second Xiangya Hospital, Central South University, Changsha 410011, China
| | - Yuqin Yin
- Department of Neurosurgery, Boston Children’s Hospital, Boston, MA 02115, USA; (L.X.); (Y.Y.)
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
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12
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Ruan Y, Cheng J, Dai J, Ma Z, Luo S, Yan R, Wang L, Zhou J, Yu B, Tong X, Shen H, Zhou L, Yuan TF, Han Q. Chronic stress hinders sensory axon regeneration via impairing mitochondrial cristae and OXPHOS. SCIENCE ADVANCES 2023; 9:eadh0183. [PMID: 37801508 PMCID: PMC10558127 DOI: 10.1126/sciadv.adh0183] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Accepted: 09/05/2023] [Indexed: 10/08/2023]
Abstract
Spinal cord injury (SCI) often leads to physical limitations, persistent pain, and major lifestyle shifts, enhancing the likelihood of prolonged psychological stress and associated disorders such as anxiety and depression. The mechanisms linking stress with regeneration remain elusive, despite understanding the detrimental impact of chronic stress on SCI recovery. In this study, we investigated the effect of chronic stress on primary sensory axon regeneration using a preconditioning lesions mouse model. Our data revealed that chronic stress-induced mitochondrial cristae loss and a decrease in oxidative phosphorylation (OXPHOS) within primary sensory neurons, impeding central axon regrowth. Corticosterone, a stress hormone, emerged as a pivotal player in this process, affecting satellite glial cells by reducing Kir4.1 expression. This led to increased neuronal hyperactivity and reactive oxygen species levels, which, in turn, deformed mitochondrial cristae and impaired OXPHOS, crucial for axonal regeneration. Our study underscores the need to manage psychological stress in patients with SCI for effective sensory-motor rehabilitation.
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Affiliation(s)
- Yu Ruan
- Songjiang Research Institute, Shanghai Songjiang District Central Hospital, Department of Anatomy and Physiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Frontiers Science Center of Cellular Homeostasis and Human Diseases, Shanghai Jiao Tong University School of Medicine, Shanghai 201600, China
| | - Jin Cheng
- Songjiang Research Institute, Shanghai Songjiang District Central Hospital, Department of Anatomy and Physiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Frontiers Science Center of Cellular Homeostasis and Human Diseases, Shanghai Jiao Tong University School of Medicine, Shanghai 201600, China
| | - Jiafeng Dai
- Department of Spine Surgery, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200127, China
| | - Zhengwen Ma
- Department of Laboratory Animal Science, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Shiyu Luo
- Songjiang Research Institute, Shanghai Songjiang District Central Hospital, Department of Anatomy and Physiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Frontiers Science Center of Cellular Homeostasis and Human Diseases, Shanghai Jiao Tong University School of Medicine, Shanghai 201600, China
| | - Run Yan
- Songjiang Research Institute, Shanghai Songjiang District Central Hospital, Department of Anatomy and Physiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Frontiers Science Center of Cellular Homeostasis and Human Diseases, Shanghai Jiao Tong University School of Medicine, Shanghai 201600, China
| | - Lizhao Wang
- Songjiang Research Institute, Shanghai Songjiang District Central Hospital, Department of Anatomy and Physiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Frontiers Science Center of Cellular Homeostasis and Human Diseases, Shanghai Jiao Tong University School of Medicine, Shanghai 201600, China
| | - Jinrui Zhou
- The Second Hospital of Jilin University, Changchun 130041, China
| | - Bin Yu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Nantong University, Nantong 226001, China
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China
| | - Xiaoping Tong
- Songjiang Research Institute, Shanghai Songjiang District Central Hospital, Department of Anatomy and Physiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Frontiers Science Center of Cellular Homeostasis and Human Diseases, Shanghai Jiao Tong University School of Medicine, Shanghai 201600, China
| | - Hongxing Shen
- Department of Spine Surgery, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200127, China
| | - Libing Zhou
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China
- Guangdong-Hongkong-Macau Institute of CNS Regeneration, Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Jinan University, Guangzhou 510632, China
| | - Ti-Fei Yuan
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai 200030, China
| | - Qi Han
- Songjiang Research Institute, Shanghai Songjiang District Central Hospital, Department of Anatomy and Physiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Frontiers Science Center of Cellular Homeostasis and Human Diseases, Shanghai Jiao Tong University School of Medicine, Shanghai 201600, China
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China
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13
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Halawani D, Wang Y, Ramakrishnan A, Estill M, He X, Shen L, Friedel RH, Zou H. Circadian clock regulator Bmal1 gates axon regeneration via Tet3 epigenetics in mouse sensory neurons. Nat Commun 2023; 14:5165. [PMID: 37620297 PMCID: PMC10449865 DOI: 10.1038/s41467-023-40816-7] [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: 10/25/2022] [Accepted: 08/11/2023] [Indexed: 08/26/2023] Open
Abstract
Axon regeneration of dorsal root ganglia (DRG) neurons after peripheral axotomy involves reconfiguration of gene regulatory circuits to establish regenerative gene programs. However, the underlying mechanisms remain unclear. Here, through an unbiased survey, we show that the binding motif of Bmal1, a central transcription factor of the circadian clock, is enriched in differentially hydroxymethylated regions (DhMRs) of mouse DRG after peripheral lesion. By applying conditional deletion of Bmal1 in neurons, in vitro and in vivo neurite outgrowth assays, as well as transcriptomic profiling, we demonstrate that Bmal1 inhibits axon regeneration, in part through a functional link with the epigenetic factor Tet3. Mechanistically, we reveal that Bmal1 acts as a gatekeeper of neuroepigenetic responses to axonal injury by limiting Tet3 expression and restricting 5hmC modifications. Bmal1-regulated genes not only concern axon growth, but also stress responses and energy homeostasis. Furthermore, we uncover an epigenetic rhythm of diurnal oscillation of Tet3 and 5hmC levels in DRG neurons, corresponding to time-of-day effect on axon growth potential. Collectively, our studies demonstrate that targeting Bmal1 enhances axon regeneration.
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Affiliation(s)
- Dalia Halawani
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Yiqun Wang
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Orthopedics, Second Affiliated Hospital of Xi'an Jiaotong University, Shaanxi, China
| | - Aarthi Ramakrishnan
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Molly Estill
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Xijing He
- Department of Orthopedics, Second Affiliated Hospital of Xi'an Jiaotong University, Shaanxi, China
- Department of Orthopedics, Xi'an International Medical Center Hospital, Xi'an, China
| | - Li Shen
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Roland H Friedel
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Hongyan Zou
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
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14
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Xie L, Yin Y, Jayakar S, Kawaguchi R, Wang Q, Peterson S, Shi C, Turnes BL, Zhang Z, Oses-Prieto J, Li J, Burlingame A, Woolf CJ, Geschwind D, Rasband M, Benowitz LI. The oncomodulin receptor ArmC10 enables axon regeneration in mice after nerve injury and neurite outgrowth in human iPSC-derived sensory neurons. Sci Transl Med 2023; 15:eadg6241. [PMID: 37556559 DOI: 10.1126/scitranslmed.adg6241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 07/21/2023] [Indexed: 08/11/2023]
Abstract
Oncomodulin (Ocm) is a myeloid cell-derived growth factor that enables axon regeneration in mice and rats after optic nerve injury or peripheral nerve injury, yet the mechanisms underlying its activity are unknown. Using proximity biotinylation, coimmunoprecipitation, surface plasmon resonance, and ectopic expression, we have identified armadillo-repeat protein C10 (ArmC10) as a high-affinity receptor for Ocm. ArmC10 deletion suppressed inflammation-induced axon regeneration in the injured optic nerves of mice. ArmC10 deletion also suppressed the ability of lesioned sensory neurons to regenerate peripheral axons rapidly after a second injury and to regenerate their central axons after spinal cord injury in mice (the conditioning lesion effect). Conversely, Ocm acted through ArmC10 to accelerate optic nerve and peripheral nerve regeneration and to enable spinal cord axon regeneration in these mouse nerve injury models. We showed that ArmC10 is highly expressed in human-induced pluripotent stem cell-derived sensory neurons and that exposure to Ocm altered gene expression and enhanced neurite outgrowth. ArmC10 was also expressed in human monocytes, and Ocm increased the expression of immune modulatory genes in these cells. These findings suggest that Ocm acting through its receptor ArmC10 may be a useful therapeutic target for nerve repair and immune modulation.
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Affiliation(s)
- Lili Xie
- Department of Neurosurgery, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
| | - Yuqin Yin
- Department of Neurosurgery, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
| | - Selwyn Jayakar
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Neurology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Riki Kawaguchi
- Departments of Neurology, Psychiatry and Human Genetics, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA
| | - Qing Wang
- Departments of Neurology, Psychiatry and Human Genetics, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA
| | - Sheri Peterson
- Department of Neurosurgery, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
| | - Caleb Shi
- Harvard College, Cambridge, MA 02138, USA
| | - Bruna Lenfers Turnes
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Neurology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Zihe Zhang
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Neurology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Juan Oses-Prieto
- Department of Pharmaceutical Chemistry, UCSF, Mission Bay Campus, San Francisco, CA, 94158, USA
| | - Jian Li
- Division of Rheumatology, Inflammation and Immunity, Brigham and Women's Hospital and Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
| | - Al Burlingame
- Department of Pharmaceutical Chemistry, UCSF, Mission Bay Campus, San Francisco, CA, 94158, USA
| | - Clifford J Woolf
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Neurology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Daniel Geschwind
- Departments of Neurology, Psychiatry and Human Genetics, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA
| | - Matthew Rasband
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - Larry I Benowitz
- Department of Neurosurgery, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA
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15
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Perez-Gianmarco L, Kukley M. Understanding the Role of the Glial Scar through the Depletion of Glial Cells after Spinal Cord Injury. Cells 2023; 12:1842. [PMID: 37508505 PMCID: PMC10377788 DOI: 10.3390/cells12141842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 06/30/2023] [Accepted: 07/11/2023] [Indexed: 07/30/2023] Open
Abstract
Spinal cord injury (SCI) is a condition that affects between 8.8 and 246 people in a million and, unlike many other neurological disorders, it affects mostly young people, causing deficits in sensory, motor, and autonomic functions. Promoting the regrowth of axons is one of the most important goals for the neurological recovery of patients after SCI, but it is also one of the most challenging goals. A key event after SCI is the formation of a glial scar around the lesion core, mainly comprised of astrocytes, NG2+-glia, and microglia. Traditionally, the glial scar has been regarded as detrimental to recovery because it may act as a physical barrier to axon regrowth and release various inhibitory factors. However, more and more evidence now suggests that the glial scar is beneficial for the surrounding spared tissue after SCI. Here, we review experimental studies that used genetic and pharmacological approaches to ablate specific populations of glial cells in rodent models of SCI in order to understand their functional role. The studies showed that ablation of either astrocytes, NG2+-glia, or microglia might result in disorganization of the glial scar, increased inflammation, extended tissue degeneration, and impaired recovery after SCI. Hence, glial cells and glial scars appear as important beneficial players after SCI.
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Affiliation(s)
- Lucila Perez-Gianmarco
- Achucarro Basque Center for Neuroscience, 48940 Leioa, PC, Spain
- Department of Neurosciences, University of the Basque Country, 48940 Leioa, PC, Spain
| | - Maria Kukley
- Achucarro Basque Center for Neuroscience, 48940 Leioa, PC, Spain
- IKERBASQUE Basque Foundation for Science, 48009 Bilbao, PC, Spain
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16
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Cheah M, Cheng Y, Petrova V, Cimpean A, Jendelova P, Swarup V, Woolf CJ, Geschwind DH, Fawcett JW. Integrin-Driven Axon Regeneration in the Spinal Cord Activates a Distinctive CNS Regeneration Program. J Neurosci 2023; 43:4775-4794. [PMID: 37277179 PMCID: PMC10312060 DOI: 10.1523/jneurosci.2076-22.2023] [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: 11/06/2022] [Revised: 04/19/2023] [Accepted: 04/21/2023] [Indexed: 06/07/2023] Open
Abstract
The peripheral branch of sensory dorsal root ganglion (DRG) neurons regenerates readily after injury unlike their central branch in the spinal cord. However, extensive regeneration and reconnection of sensory axons in the spinal cord can be driven by the expression of α9 integrin and its activator kindlin-1 (α9k1), which enable axons to interact with tenascin-C. To elucidate the mechanisms and downstream pathways affected by activated integrin expression and central regeneration, we conducted transcriptomic analyses of adult male rat DRG sensory neurons transduced with α9k1, and controls, with and without axotomy of the central branch. Expression of α9k1 without the central axotomy led to upregulation of a known PNS regeneration program, including many genes associated with peripheral nerve regeneration. Coupling α9k1 treatment with dorsal root axotomy led to extensive central axonal regeneration. In addition to the program upregulated by α9k1 expression, regeneration in the spinal cord led to expression of a distinctive CNS regeneration program, including genes associated with ubiquitination, autophagy, endoplasmic reticulum (ER), trafficking, and signaling. Pharmacological inhibition of these processes blocked the regeneration of axons from DRGs and human iPSC-derived sensory neurons, validating their causal contributions to sensory regeneration. This CNS regeneration-associated program showed little correlation with either embryonic development or PNS regeneration programs. Potential transcriptional drivers of this CNS program coupled to regeneration include Mef2a, Runx3, E2f4, and Yy1. Signaling from integrins primes sensory neurons for regeneration, but their axon growth in the CNS is associated with an additional distinctive program that differs from that involved in PNS regeneration.SIGNIFICANCE STATEMENT Restoration of neurologic function after spinal cord injury has yet to be achieved in human patients. To accomplish this, severed nerve fibers must be made to regenerate. Reconstruction of nerve pathways has not been possible, but recently, a method for stimulating long-distance axon regeneration of sensory fibers in rodents has been developed. This research uses profiling of messenger RNAs in the regenerating sensory neurons to discover which mechanisms are activated. This study shows that the regenerating neurons initiate a novel CNS regeneration program which includes molecular transport, autophagy, ubiquitination, and modulation of the endoplasmic reticulum (ER). The study identifies mechanisms that neurons need to activate to regenerate their nerve fibers.
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Affiliation(s)
- Menghon Cheah
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0PY, United Kingdom
| | - Yuyan Cheng
- Program in Neurogenetics, Department of Neurology, and Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095
| | - Veselina Petrova
- Department of Neurobiology, Harvard Medical School; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts 02115
| | - Anda Cimpean
- Centre for Reconstructive Neuroscience, Institute of Experimental Medicine Czech Academy of Science, Prague, Czech Republic
| | - Pavla Jendelova
- Centre for Reconstructive Neuroscience, Institute of Experimental Medicine Czech Academy of Science, Prague, Czech Republic
| | - Vivek Swarup
- Program in Neurogenetics, Department of Neurology, and Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095
- Department of Neurobiology and Behavior, University of California, Irvine, California 92697
| | - Clifford J Woolf
- Department of Neurobiology, Harvard Medical School; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts 02115
| | - Daniel H Geschwind
- Program in Neurogenetics, Department of Neurology, and Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095
| | - James W Fawcett
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0PY, United Kingdom
- Centre for Reconstructive Neuroscience, Institute of Experimental Medicine Czech Academy of Science, Prague, Czech Republic
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17
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Gupta S, Dutta S, Hui SP. Regenerative Potential of Injured Spinal Cord in the Light of Epigenetic Regulation and Modulation. Cells 2023; 12:1694. [PMID: 37443728 PMCID: PMC10341208 DOI: 10.3390/cells12131694] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 06/13/2023] [Accepted: 06/17/2023] [Indexed: 07/15/2023] Open
Abstract
A spinal cord injury is a form of physical harm imposed on the spinal cord that causes disability and, in many cases, leads to permanent mammalian paralysis, which causes a disastrous global issue. Because of its non-regenerative aspect, restoring the spinal cord's role remains one of the most daunting tasks. By comparison, the remarkable regenerative ability of some regeneration-competent species, such as some Urodeles (Axolotl), Xenopus, and some teleost fishes, enables maximum functional recovery, even after complete spinal cord transection. During the last two decades of intensive research, significant progress has been made in understanding both regenerative cells' origins and the molecular signaling mechanisms underlying the regeneration and reconstruction of damaged spinal cords in regenerating organisms and mammals, respectively. Epigenetic control has gradually moved into the center stage of this research field, which has been helped by comprehensive work demonstrating that DNA methylation, histone modifications, and microRNAs are important for the regeneration of the spinal cord. In this review, we concentrate primarily on providing a comparison of the epigenetic mechanisms in spinal cord injuries between non-regenerating and regenerating species. In addition, we further discuss the epigenetic mediators that underlie the development of a regeneration-permissive environment following injury in regeneration-competent animals and how such mediators may be implicated in optimizing treatment outcomes for spinal cord injurie in higher-order mammals. Finally, we briefly discuss the role of extracellular vesicles (EVs) in the context of spinal cord injury and their potential as targets for therapeutic intervention.
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Affiliation(s)
- Samudra Gupta
- S.N. Pradhan Centre for Neurosciences, University of Calcutta, 35, Ballygunge Circular Road, Kolkata 700019, India;
| | - Suman Dutta
- Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, UK;
| | - Subhra Prakash Hui
- S.N. Pradhan Centre for Neurosciences, University of Calcutta, 35, Ballygunge Circular Road, Kolkata 700019, India;
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18
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Martinez-Torres S, Mesquida-Veny F, Del Rio JA, Hervera A. Injury-induced activation of the endocannabinoid system promotes axon regeneration. iScience 2023; 26:106814. [PMID: 37235048 PMCID: PMC10205787 DOI: 10.1016/j.isci.2023.106814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/31/2023] [Accepted: 05/01/2023] [Indexed: 05/28/2023] Open
Abstract
Regeneration after a peripheral nerve injury still remains a challenge, due to the limited regenerative potential of axons after injury. While the endocannabinoid system (ECS) has been widely studied for its neuroprotective and analgesic effects, its role in axonal regeneration and during the conditioning lesion remains unexplored. In this study, we observed that a peripheral nerve injury induces axonal regeneration through an increase in the endocannabinoid tone. We also enhanced the regenerative capacity of dorsal root ganglia (DRG) neurons through the inhibition of endocannabinoid degradative enzyme MAGL or a CB1R agonist. Our results suggest that the ECS, via CB1R and PI3K-pAkt pathway activation, plays an important role in promoting the intrinsic regenerative capacity of sensory neurons after injury.
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Affiliation(s)
- Sara Martinez-Torres
- Molecular and Cellular Neurobiotechnology, Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain
- Department of Cell Biology, Physiology and Immunology, University of Barcelona, Barcelona, Spain
- Network Centre of Biomedical Research of Neurodegenerative Diseases (CIBERNED), Institute of Health Carlos III, Ministry of Economy and Competitiveness, Madrid, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
| | - Francina Mesquida-Veny
- Molecular and Cellular Neurobiotechnology, Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain
- Department of Cell Biology, Physiology and Immunology, University of Barcelona, Barcelona, Spain
- Network Centre of Biomedical Research of Neurodegenerative Diseases (CIBERNED), Institute of Health Carlos III, Ministry of Economy and Competitiveness, Madrid, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
| | - José Antonio Del Rio
- Molecular and Cellular Neurobiotechnology, Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain
- Department of Cell Biology, Physiology and Immunology, University of Barcelona, Barcelona, Spain
- Network Centre of Biomedical Research of Neurodegenerative Diseases (CIBERNED), Institute of Health Carlos III, Ministry of Economy and Competitiveness, Madrid, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
| | - Arnau Hervera
- Molecular and Cellular Neurobiotechnology, Institute for Bioengineering of Catalonia (IBEC), Barcelona, Spain
- Department of Cell Biology, Physiology and Immunology, University of Barcelona, Barcelona, Spain
- Network Centre of Biomedical Research of Neurodegenerative Diseases (CIBERNED), Institute of Health Carlos III, Ministry of Economy and Competitiveness, Madrid, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
- Clinical Neuroimmunology Group, Vall Hebron Research Institute (VHIR), Barcelona, Spain
- Multiple Sclerosis Centre of Catalonia (CEM-CAT), Barcelona, Spain
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19
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Yuan W, Liu W, Zhan X, Zhou Y, Ma R, Liang S, Wang T, Ge Z. Inhibition of miR-221-3p promotes axonal regeneration and repair of primary sensory neurons via regulating p27 expression. Neuroreport 2023; 34:471-484. [PMID: 37161985 PMCID: PMC10292576 DOI: 10.1097/wnr.0000000000001912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Accepted: 04/12/2023] [Indexed: 05/11/2023]
Abstract
This study aimed to explore the key microRNA (miRNA) playing a vital role in axonal regeneration with a hostile microenvironment after spinal cord injury. Based on the theory that sciatic nerve conditioning injury (SNCI) could promote the repair of the injured dorsal column. Differentially expressed miRNAs were screened according to the microarray, revealing that 47 known miRNAs were differentially expressed after injury and perhaps involved in nerve regeneration. Among the 47 miRNAs, the expression of miR-221-3p decreased sharply in the SNCI group compared with the simple dorsal column lesion (SDCL) group. Subsequently, it was confirmed that p27 was the target gene of miR-221-3p from luciferase reporter assay. Further, we found that inhibition of miR-221-3p expression could specifically target p27 to upregulate the expression of growth-associated protein 43 (GAP-43), α-tubulin acetyltransferase (α-TAT1) together with α-tubulin, and advance the regeneration of dorsal root ganglion (DRG) neuronal axons. Chondroitin sulfate proteoglycans (CSPGs) are the main components of glial scar, which can hinder the extension and growth of damaged neuronal axons. After CSPGs were used in this study, the results demonstrated that restrained miR-221-3p expression also via p27 promoted the upregulation of GAP-43, α-TAT1, and α-tubulin and enhanced the axonal growth of DRG neurons. Hence, miR-221-3p could contribute significantly to the regeneration of DRG neurons by specifically regulating p27 in the p27/CDK2/GAP-43 and p27/α-TAT1/α-tubulin pathways even in the inhibitory environment with CSPGs.
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Affiliation(s)
- Wenqi Yuan
- Department of Orthopedic Surgery, General Hospital of Ningxia Medical University
| | - Wei Liu
- School of Clinical Medicine, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region
| | - Xuehua Zhan
- Department of Orthopedic Surgery, General Hospital of Ningxia Medical University
| | - Yueyong Zhou
- School of Clinical Medicine, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region
| | - Rong Ma
- Department of Orthopedic Surgery, General Hospital of Ningxia Medical University
| | - Simin Liang
- Department of Orthopedic Surgery, General Hospital of Ningxia Medical University
| | - Tianyi Wang
- Department of Spine Surgery, 981st Hospital of the Chinese People’s Liberation Army Joint Logistics Support Force, Chengde, China
| | - Zhaohui Ge
- Department of Orthopedic Surgery, General Hospital of Ningxia Medical University
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20
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Decourt C, Schaeffer J, Blot B, Paccard A, Excoffier B, Pende M, Nawabi H, Belin S. The RSK2-RPS6 axis promotes axonal regeneration in the peripheral and central nervous systems. PLoS Biol 2023; 21:e3002044. [PMID: 37068088 PMCID: PMC10109519 DOI: 10.1371/journal.pbio.3002044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 02/21/2023] [Indexed: 04/18/2023] Open
Abstract
Unlike immature neurons and the ones from the peripheral nervous system (PNS), mature neurons from the central nervous system (CNS) cannot regenerate after injury. In the past 15 years, tremendous progress has been made to identify molecules and pathways necessary for neuroprotection and/or axon regeneration after CNS injury. In most regenerative models, phosphorylated ribosomal protein S6 (p-RPS6) is up-regulated in neurons, which is often associated with an activation of the mTOR (mammalian target of rapamycin) pathway. However, the exact contribution of posttranslational modifications of this ribosomal protein in CNS regeneration remains elusive. In this study, we demonstrate that RPS6 phosphorylation is essential for PNS and CNS regeneration in mice. We show that this phosphorylation is induced during the preconditioning effect in dorsal root ganglion (DRG) neurons and that it is controlled by the p90S6 kinase RSK2. Our results reveal that RSK2 controls the preconditioning effect and that the RSK2-RPS6 axis is key for this process, as well as for PNS regeneration. Finally, we demonstrate that RSK2 promotes CNS regeneration in the dorsal column, spinal cord synaptic plasticity, and target innervation leading to functional recovery. Our data establish the critical role of RPS6 phosphorylation controlled by RSK2 in CNS regeneration and give new insights into the mechanisms related to axon growth and circuit formation after traumatic lesion.
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Affiliation(s)
- Charlotte Decourt
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
| | - Julia Schaeffer
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
| | - Beatrice Blot
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
| | - Antoine Paccard
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
| | - Blandine Excoffier
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
| | - Mario Pende
- Institut Necker Enfants Malades, INSERM U1151, Université de Paris, Paris, France
| | - Homaira Nawabi
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
| | - Stephane Belin
- Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut Neurosciences, 38000 Grenoble, France
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21
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Resurgent neuropathic discharge: an obstacle to the therapeutic use of neuroma resection? Pain 2023; 164:349-361. [PMID: 35639421 DOI: 10.1097/j.pain.0000000000002704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 05/20/2022] [Indexed: 02/06/2023]
Abstract
ABSTRACT Ectopic discharge ("ectopia") in damaged afferent axons is a major contributor to chronic neuropathic pain. Clinical opinion discourages surgical resection of nerves proximal to the original injury site for fear of resurgence of ectopia and exacerbated pain. We tested this concept in a well-established animal neuroma model. Teased-fiber recordings were made of ectopic spontaneous discharge originating in the experimental nerve-end neuroma and associated dorsal root ganglia in rats that underwent either a single transection (with ligation) of the sciatic nerve or 2 consecutive transections separated by 7, 14, 21, or 30 days. Ectopia emerged in afferent A and C fibers after a single cut with kinetics anticipated from previous studies. When resection was performed during the early period of intense A-fiber activity, a brief period of resurgence was observed. However, resection of neuromas of more than 14 days was followed by low levels of activity with no indication of resurgence. This remained the case in trials out to 60 days after the first cut. Similarly, we saw no indication of resurgent ectopia originating in axotomized dorsal root ganglion neuronal somata and no behavioral reflection of resurgence. In summary, we failed to validate the concern that proximal resection of a problematic nerve would lead to intense resurgent ectopic discharge and pain. As the well-entrenched concept of resurgence is based more on case reports and anecdotes than on solid evidence, it may be justified to relax the stricture against resecting neuromas as a therapeutic strategy, at least within the framework of controlled clinical trials.
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22
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Wang X, Yang C, Wang X, Miao J, Chen W, Zhou Y, Xu Y, An Y, Cheng A, Ye W, Chen M, Song D, Yuan X, Wang J, Qian P, Ruohao Wu A, Zhang ZY, Liu K. Driving axon regeneration by orchestrating neuronal and non-neuronal innate immune responses via the IFNγ-cGAS-STING axis. Neuron 2023; 111:236-255.e7. [PMID: 36370710 PMCID: PMC9851977 DOI: 10.1016/j.neuron.2022.10.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 09/20/2022] [Accepted: 10/18/2022] [Indexed: 11/13/2022]
Abstract
The coordination mechanism of neural innate immune responses for axon regeneration is not well understood. Here, we showed that neuronal deletion of protein tyrosine phosphatase non-receptor type 2 sustains the IFNγ-STAT1 activity in retinal ganglion cells (RGCs) to promote axon regeneration after injury, independent of mTOR or STAT3. DNA-damage-induced cGAMP synthase (cGAS)-stimulator of interferon genes (STINGs) activation is the functional downstream signaling. Directly activating neuronal STING by cGAMP promotes axon regeneration. In contrast to the central axons, IFNγ is locally translated in the injured peripheral axons and upregulates cGAS expression in Schwann cells and infiltrating blood cells to produce cGAMP, which promotes spontaneous axon regeneration as an immunotransmitter. Our study demonstrates that injured peripheral nervous system (PNS) axons can direct the environmental innate immune response for self-repair and that the neural antiviral mechanism can be harnessed to promote axon regeneration in the central nervous system (CNS).
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Affiliation(s)
- Xu Wang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China,Hong Kong Center for Neurodegenerative Diseases, Hong Kong, China,Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China,Biomedical Research Institute, Shenzhen Peking University–The Hong Kong University of Science and Technology Medical Center, Shenzhen 518036, China,Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen-Hong Kong Institute of Brain Science, Shenzhen, Guangdong 518057, China,Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou 510515, China,These authors contributed equally
| | - Chao Yang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China,Hong Kong Center for Neurodegenerative Diseases, Hong Kong, China,Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China,Biomedical Research Institute, Shenzhen Peking University–The Hong Kong University of Science and Technology Medical Center, Shenzhen 518036, China,Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen-Hong Kong Institute of Brain Science, Shenzhen, Guangdong 518057, China,Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou 510515, China,These authors contributed equally
| | - Xuejie Wang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China,Hong Kong Center for Neurodegenerative Diseases, Hong Kong, China
| | - Jinmin Miao
- Department of Medicinal Chemistry and Molecular Pharmacology, Department of Chemistry, Center for Cancer Research and Institute for Drug Discovery, Purdue University, West Lafayette, IN, USA
| | - Weitao Chen
- Biomedical Research Institute, Shenzhen Peking University–The Hong Kong University of Science and Technology Medical Center, Shenzhen 518036, China
| | - Yiren Zhou
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Ying Xu
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China,Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Yongyan An
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Aifang Cheng
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China,Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Wenkang Ye
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China,Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Mengxian Chen
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Dong Song
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China,Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Xue Yuan
- Hong Kong Center for Neurodegenerative Diseases, Hong Kong, China
| | - Jiguang Wang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China,Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Peiyuan Qian
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China,Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Angela Ruohao Wu
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China,Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China,Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, China,Center for Aging Science, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Zhong-Yin Zhang
- Department of Medicinal Chemistry and Molecular Pharmacology, Department of Chemistry, Center for Cancer Research and Institute for Drug Discovery, Purdue University, West Lafayette, IN, USA
| | - Kai Liu
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong, China; Hong Kong Center for Neurodegenerative Diseases, Hong Kong, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China; Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen 518036, China; Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen-Hong Kong Institute of Brain Science, Shenzhen, Guangdong 518057, China; Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou 510515, China.
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23
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Zheng B, Tuszynski MH. Regulation of axonal regeneration after mammalian spinal cord injury. Nat Rev Mol Cell Biol 2023; 24:396-413. [PMID: 36604586 DOI: 10.1038/s41580-022-00562-y] [Citation(s) in RCA: 48] [Impact Index Per Article: 48.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2022] [Indexed: 01/06/2023]
Abstract
One hundred years ago, Ramón y Cajal, considered by many as the founder of modern neuroscience, stated that neurons of the adult central nervous system (CNS) are incapable of regenerating. Yet, recent years have seen a tremendous expansion of knowledge in the molecular control of axon regeneration after CNS injury. We now understand that regeneration in the adult CNS is limited by (1) a failure to form cellular or molecular substrates for axon attachment and elongation through the lesion site; (2) environmental factors, including inhibitors of axon growth associated with myelin and the extracellular matrix; (3) astrocyte responses, which can both limit and support axon growth; and (4) intraneuronal mechanisms controlling the establishment of an active cellular growth programme. We discuss these topics together with newly emerging hypotheses, including the surprising finding from transcriptomic analyses of the corticospinal system in mice that neurons revert to an embryonic state after spinal cord injury, which can be sustained to promote regeneration with neural stem cell transplantation. These gains in knowledge are steadily advancing efforts to develop effective treatment strategies for spinal cord injury in humans.
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Affiliation(s)
- Binhai Zheng
- Department of Neurosciences, School of Medicine, University of California San Diego, La Jolla, CA, USA. .,VA San Diego Research Service, San Diego, CA, USA.
| | - Mark H Tuszynski
- Department of Neurosciences, School of Medicine, University of California San Diego, La Jolla, CA, USA. .,VA San Diego Research Service, San Diego, CA, USA.
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24
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Omura T. Editorial: Axonal growth in normal and pathological conditions. Front Mol Neurosci 2022; 15:1107999. [PMID: 36583083 PMCID: PMC9792978 DOI: 10.3389/fnmol.2022.1107999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 11/28/2022] [Indexed: 12/15/2022] Open
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25
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Cao HJ, Huang L, Zheng MR, Zhang T, Xu LC. Characterization of circular RNAs in dorsal root ganglia after central and peripheral axon injuries. Front Cell Neurosci 2022; 16:1046050. [PMID: 36578373 PMCID: PMC9790916 DOI: 10.3389/fncel.2022.1046050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 11/28/2022] [Indexed: 12/14/2022] Open
Abstract
In central nervous system, axons fail to regenerate after injury while in peripheral nervous system, axons retain certain regenerative ability. Dorsal root ganglion (DRG) neuron has an ascending central axon branch and a descending peripheral axon branch stemming from one single axon and serves as a suitable model for the comparison of growth competence following central and peripheral axon injuries. Molecular alterations underpin different injury responses of DRG branches have been investigated from many aspects, such as coding gene expression, chromatin accessibility, and histone acetylation. However, changes of circular RNAs are poorly characterized. In the present study, we comprehensively investigate circular RNA expressions in DRGs after rat central and peripheral axon injuries using sequencing analysis and identify a total of 33 differentially expressed circular RNAs after central branch injury as well as 55 differentially expressed circular RNAs after peripheral branch injury. Functional enrichment of host genes of differentially expressed circular RNAs demonstrate the participation of Hippo signaling pathway and Notch signaling pathway after both central and peripheral axon injuries. Circular RNA changes after central axon injury are also linked with apoptosis and cellular junction while changes after peripheral axon injury are associated with metabolism and PTEN-related pathways. Altogether, the present study offers a systematic evaluation of alterations of circular RNAs in rat DRGs following injuries to the central and peripheral axon branches and contributes to the deciphering of essential biological activities and mechanisms behind successful nerve regeneration.
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Affiliation(s)
- Hong-Jun Cao
- Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Li Huang
- Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Meng-Ru Zheng
- Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Tao Zhang
- School of Medicine and Holistic Integrative Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China
| | - Ling-Chi Xu
- Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China,*Correspondence: Ling-Chi Xu,
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26
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Intrinsic heterogeneity in axon regeneration. Biochem Soc Trans 2022; 50:1753-1762. [DOI: 10.1042/bst20220624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 11/01/2022] [Accepted: 11/07/2022] [Indexed: 11/18/2022]
Abstract
The nervous system is composed of a variety of neurons and glial cells with different morphology and functions. In the mammalian peripheral nervous system (PNS) or the lower vertebrate central nervous system (CNS), most neurons can regenerate extensively after axotomy, while the neurons in the mammalian CNS possess only limited regenerative ability. This heterogeneity is common within and across species. The studies about the transcriptomes after nerve injury in different animal models have revealed a series of molecular and cellular events that occurred in neurons after axotomy. However, responses of various types of neurons located in different positions of individuals were different remarkably. Thus, researchers aim to find the key factors that are conducive to regeneration, so as to provide the molecular basis for solving the regeneration difficulties after CNS injury. Here we review the heterogeneity of axonal regeneration among different cell subtypes in different animal models or the same organ, emphasizing the importance of comparative studies within and across species.
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27
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A small molecule M1 promotes optic nerve regeneration to restore target-specific neural activity and visual function. Proc Natl Acad Sci U S A 2022; 119:e2121273119. [PMID: 36306327 PMCID: PMC9636930 DOI: 10.1073/pnas.2121273119] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Axon regeneration is an energy-demanding process that requires active mitochondrial transport. In contrast to the central nervous system (CNS), axonal mitochondrial transport in regenerating axons of the peripheral nervous system (PNS) increases within hours and sustains for weeks after injury. Yet, little is known about targeting mitochondria in nervous system repair. Here, we report the induction of sustained axon regeneration, neural activities in the superior colliculus (SC), and visual function recovery after optic nerve crush (ONC) by M1, a small molecule that promotes mitochondrial fusion and transport. We demonstrated that M1 enhanced mitochondrial dynamics in cultured neurons and accelerated in vivo axon regeneration in the PNS. Ex vivo time-lapse imaging and kymograph analysis showed that M1 greatly increased mitochondrial length, axonal mitochondrial motility, and transport velocity in peripheral axons of the sciatic nerves. Following ONC, M1 increased the number of axons regenerating through the optic chiasm into multiple subcortical areas and promoted the recovery of local field potentials in the SC after optogenetic stimulation of retinal ganglion cells, resulting in complete recovery of the pupillary light reflex, and restoration of the response to looming visual stimuli was detected. M1 increased the gene expression of mitochondrial fusion proteins and major axonal transport machinery in both the PNS and CNS neurons without inducing inflammatory responses. The knockdown of two key mitochondrial genes,
Opa1
or
Mfn2
, abolished the growth-promoting effects of M1 after ONC, suggesting that maintaining a highly dynamic mitochondrial population in axons is required for successful CNS axon regeneration.
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28
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Kwon MJ, Seo Y, Cho H, Kim HS, Oh YJ, Genişcan S, Kim M, Park HH, Joe EH, Kwon MH, Kang HC, Kim BG. Nanogel-mediated delivery of oncomodulin secreted from regeneration-associated macrophages promotes sensory axon regeneration in the spinal cord. Theranostics 2022; 12:5856-5876. [PMID: 35966584 PMCID: PMC9373827 DOI: 10.7150/thno.73386] [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: 03/29/2022] [Accepted: 07/20/2022] [Indexed: 11/06/2022] Open
Abstract
Preconditioning nerve injury enhances axonal regeneration of dorsal root ganglia (DRG) neurons in part by driving pro-regenerative perineuronal macrophage activation. How these macrophages influence the neuronal capacity of axon regeneration remains elusive. We report that oncomodulin (ONCM) is produced from the regeneration-associated macrophages and strongly influences regeneration of DRG sensory axons. We also attempted to promote sensory axon regeneration by nanogel-mediated delivery of ONCM to DRGs. Methods:In vitro neuron-macrophage interaction model and preconditioning sciatic nerve injury were used to verify the necessity of ONCM in preconditioning injury-induced neurite outgrowth. We developed a nanogel-mediated delivery system in which electrostatic encapsulation of ONCM by a reducible epsilon-poly(L-lysine)-nanogel (REPL-NG) enabled a controlled release of ONCM. Results: Sciatic nerve injury upregulated ONCM in DRG macrophages. ONCM in macrophages was necessary to produce pro-regenerative macrophages in the in vitro model of neuron-macrophage interaction and played an essential role in preconditioning-induced neurite outgrowth. ONCM increased neurite outgrowth in cultured DRG neurons by activating a distinct gene set, particularly neuropeptide-related genes. Increasing extracellularly secreted ONCM in DRGs sufficiently enhanced the capacity of neurite outgrowth. Intraganglionic injection of REPL-NG/ONCM complex allowed sustained ONCM activity in DRG tissue and achieved a remarkable long-range regeneration of dorsal column sensory axons beyond spinal cord lesion. Conclusion: NG-mediated ONCM delivery could be exploited as a therapeutic strategy for promoting sensory axon regeneration following spinal cord injury.
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Affiliation(s)
- Min Jung Kwon
- Department of Brain Science, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,AI-Superconvergence KIURI Translational Research Center, Suwon, 16499, Republic of Korea
| | - Yeojin Seo
- Department of Brain Science, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea
| | - Hana Cho
- Department of Pharmacy, College of Pharmacy, The Catholic University of Korea, Bucheon, 14662, Republic of Korea
| | - Hyung Soon Kim
- Department of Brain Science, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea
| | - Young Joo Oh
- Department of Brain Science, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea
| | - Simay Genişcan
- Department of Brain Science, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea
| | - Minjae Kim
- Department of Microbiology, Ajou University School of Medicine, Suwon 16499, Republic of Korea
| | - Hee Hwan Park
- Department of Brain Science, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea
| | - Eun-Hye Joe
- Department of Brain Science, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,Department of Pharmacology, Ajou University School of Medicine, Suwon, 16499, Republic of Korea.,Center for Convergence Research of Neurological Disorders, Ajou University School of Medicine, Suwon, 16499, Republic of Korea
| | - Myung-Hee Kwon
- Department of Microbiology, Ajou University School of Medicine, Suwon 16499, Republic of Korea
| | - Han Chang Kang
- Department of Pharmacy, College of Pharmacy, The Catholic University of Korea, Bucheon, 14662, Republic of Korea
| | - Byung Gon Kim
- Department of Brain Science, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,Neuroscience Graduate Program, Department of Biomedical Sciences, Ajou University Graduate School of Medicine, Suwon, 16499, Republic of Korea.,Center for Convergence Research of Neurological Disorders, Ajou University School of Medicine, Suwon, 16499, Republic of Korea.,Department of Neurology, Ajou University School of Medicine, Suwon, 16499, Republic of Korea.,AI-Superconvergence KIURI Translational Research Center, Suwon, 16499, Republic of Korea
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29
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Jacobi A, Tran NM, Yan W, Benhar I, Tian F, Schaffer R, He Z, Sanes JR. Overlapping transcriptional programs promote survival and axonal regeneration of injured retinal ganglion cells. Neuron 2022; 110:2625-2645.e7. [PMID: 35767994 PMCID: PMC9391321 DOI: 10.1016/j.neuron.2022.06.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 04/08/2022] [Accepted: 06/03/2022] [Indexed: 12/12/2022]
Abstract
Injured neurons in the adult mammalian central nervous system often die and seldom regenerate axons. To uncover transcriptional pathways that could ameliorate these disappointing responses, we analyzed three interventions that increase survival and regeneration of mouse retinal ganglion cells (RGCs) following optic nerve crush (ONC) injury, albeit not to a clinically useful extent. We assessed gene expression in each of 46 RGC types by single-cell transcriptomics following ONC and treatment. We also compared RGCs that regenerated with those that survived but did not regenerate. Each intervention enhanced survival of most RGC types, but type-independent axon regeneration required manipulation of multiple pathways. Distinct computational methods converged on separate sets of genes selectively expressed by RGCs likely to be dying, surviving, or regenerating. Overexpression of genes associated with the regeneration program enhanced both survival and axon regeneration in vivo, indicating that mechanistic analysis can be used to identify novel therapeutic strategies.
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Affiliation(s)
- Anne Jacobi
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA; Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA
| | - Nicholas M Tran
- Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Wenjun Yan
- Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA
| | - Inbal Benhar
- Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - Feng Tian
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Rebecca Schaffer
- Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA
| | - Zhigang He
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, and Department of Neurology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
| | - Joshua R Sanes
- Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA.
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30
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Noristani HN. Intrinsic regulation of axon regeneration after spinal cord injury: Recent advances and remaining challenges. Exp Neurol 2022; 357:114198. [DOI: 10.1016/j.expneurol.2022.114198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 07/20/2022] [Accepted: 08/02/2022] [Indexed: 11/16/2022]
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31
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Zhang S, Zhu H, Pan Y, Liu X, Jin H, Nan K, Wu W. Exploration of the strategies to enhance the regeneration of the optic nerve. Exp Eye Res 2022; 219:109068. [DOI: 10.1016/j.exer.2022.109068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 03/24/2022] [Accepted: 04/03/2022] [Indexed: 11/26/2022]
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32
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Noristani HN, Kim H, Pang S, Zhong J, Son YJ. Co-targeting B-RAF and PTEN Enables Sensory Axons to Regenerate Across and Beyond the Spinal Cord Injury. Front Mol Neurosci 2022; 15:891463. [PMID: 35557554 PMCID: PMC9087900 DOI: 10.3389/fnmol.2022.891463] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 03/30/2022] [Indexed: 11/25/2022] Open
Abstract
Primary sensory axons in adult mammals fail to regenerate after spinal cord injury (SCI), in part due to insufficient intrinsic growth potential. Robustly boosting their growth potential continues to be a challenge. Previously, we showed that constitutive activation of B-RAF (rapidly accelerated fibrosarcoma kinase) markedly promotes axon regeneration after dorsal root and optic nerve injuries. The regrowth is further augmented by supplemental deletion of PTEN (phosphatase and tensin homolog). Here, we examined whether concurrent B-RAF activation and PTEN deletion promotes dorsal column axon regeneration after SCI. Remarkably, genetically targeting B-RAF and PTEN selectively in DRG neurons of adult mice enables many DC axons to enter, cross, and grow beyond the lesion site after SCI; some axons reach ∼2 mm rostral to the lesion by 3 weeks post-injury. Co-targeting B-RAF and PTEN promotes more robust DC regeneration than a pre-conditioning lesion, which additively enhances the regeneration triggered by B-RAF/PTEN. We also found that post-injury targeting of B-RAF and PTEN enhances DC axon regeneration. These results demonstrate that co-targeting B-RAF and PTEN effectively enhances the intrinsic growth potential of DC axons after SCI and therefore may help to develop a novel strategy to promote robust long-distance regeneration of primary sensory axons.
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Affiliation(s)
- Harun N. Noristani
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
- *Correspondence: Harun N. Noristani,
| | - Hyukmin Kim
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Shuhuan Pang
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
| | - Jian Zhong
- Burke Medical Research Institute, Weill Cornell Medical College of Cornell University, White Plains, NY, United States
| | - Young-Jin Son
- Shriners Hospitals Pediatric Research Center and Center for Neural Repair, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
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Zhang J, Jiang C, Liu X, Jiang CX, Cao Q, Yu B, Ni Y, Mao S. The metabolomic profiling identifies N, N-dimethylglycine as a facilitator of dorsal root ganglia neuron axon regeneration after injury. FASEB J 2022; 36:e22305. [PMID: 35394692 DOI: 10.1096/fj.202101698r] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Revised: 03/02/2022] [Accepted: 03/28/2022] [Indexed: 11/11/2022]
Abstract
Identifying novel molecules involved in axon regeneration of neurons in the peripheral nervous system (PNS) will be of benefit in obtaining a therapeutic strategy for repairing axon damage both in the PNS and the central nervous system (CNS). Metabolism and axon regeneration are tightly connected. However, the overall metabolic processes and the landscape of the metabolites in axon regeneration of PNS neurons are uncovered. Here, we used an ultra high performance liquid tandem chromatography quadrupole time of flight mass spectrometry (UHPLC-QTOFMS)-based untargeted metabolomics to analyze dorsal root ganglia (DRG) metabolic characteristics at different time points post sciatic nerve injury and acquired hundreds of differentially changed metabolites. In addition, the results reveal that several metabolic pathways were significantly altered, such as 'Histidine metabolism', 'Glycine serine and threonine metabolism', 'Arginine and proline metabolism', 'taurine and hypotaurine metabolism' and so on. Given metabolite could alter a cell's or an organism's phenotype, further investigation demonstrated that N, N-dimethylglycine (DMG) has a promoting effect on the regenerative ability post injury. Overall, our data may serve as a resource useful for further understanding how metabolites contribute to axon regeneration in DRG during sciatic nerve regeneration and suggest DMG may be a candidate drug to repair nerve injury.
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Affiliation(s)
- Junjie Zhang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Chunyi Jiang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China.,Department of Pathology, Affiliated Hospital of Nantong University, Nantong, China
| | - Xiaohong Liu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | | | - Qianqian Cao
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Bin Yu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Yaohui Ni
- Department of Neurology, Affiliated Hospital of Nantong University, Nantong, China
| | - Susu Mao
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
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34
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Winter CC, He Z, Jacobi A. Axon Regeneration: A Subcellular Extension in Multiple Dimensions. Cold Spring Harb Perspect Biol 2022; 14:a040923. [PMID: 34518340 PMCID: PMC8886981 DOI: 10.1101/cshperspect.a040923] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Axons are a unique cellular structure that allows for the communication between neurons. Axon damage compromises neuronal communications and often leads to functional deficits. Thus, developing strategies that promote effective axon regeneration for functional restoration is highly desirable. One fruitful approach is to dissect the regenerative mechanisms used by some types of neurons in both mammalian and nonmammalian systems that exhibit spontaneous regenerative capacity. Additionally, numerous efforts have been devoted to deciphering the barriers that prevent successful axon regeneration in the most regeneration-refractory system-the adult mammalian central nervous system. As a result, several regeneration-promoting strategies have been developed, but significant limitations remain. This review is aimed to summarize historic progression and current understanding of this exciting yet incomplete endeavor.
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Affiliation(s)
- Carla C Winter
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts 02115, USA
- Department of Neurology and Ophthalmology, Harvard Medical School, Boston, Massachusetts 02115, USA
- PhD Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Zhigang He
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts 02115, USA
- Department of Neurology and Ophthalmology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Anne Jacobi
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts 02115, USA
- Department of Neurology and Ophthalmology, Harvard Medical School, Boston, Massachusetts 02115, USA
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35
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Varadarajan SG, Hunyara JL, Hamilton NR, Kolodkin AL, Huberman AD. Central nervous system regeneration. Cell 2022; 185:77-94. [PMID: 34995518 PMCID: PMC10896592 DOI: 10.1016/j.cell.2021.10.029] [Citation(s) in RCA: 75] [Impact Index Per Article: 37.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/26/2021] [Accepted: 10/27/2021] [Indexed: 02/06/2023]
Abstract
Neurons of the mammalian central nervous system fail to regenerate. Substantial progress has been made toward identifying the cellular and molecular mechanisms that underlie regenerative failure and how altering those pathways can promote cell survival and/or axon regeneration. Here, we summarize those findings while comparing the regenerative process in the central versus the peripheral nervous system. We also highlight studies that advance our understanding of the mechanisms underlying neural degeneration in response to injury, as many of these mechanisms represent primary targets for restoring functional neural circuits.
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Affiliation(s)
| | - John L Hunyara
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Natalie R Hamilton
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Alex L Kolodkin
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Andrew D Huberman
- Department of Neurobiology, Stanford University, Stanford, CA 94305, USA; Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA.
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Hilton BJ, Husch A, Schaffran B, Lin TC, Burnside ER, Dupraz S, Schelski M, Kim J, Müller JA, Schoch S, Imig C, Brose N, Bradke F. An active vesicle priming machinery suppresses axon regeneration upon adult CNS injury. Neuron 2022; 110:51-69.e7. [PMID: 34706221 PMCID: PMC8730507 DOI: 10.1016/j.neuron.2021.10.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 09/03/2021] [Accepted: 10/01/2021] [Indexed: 12/16/2022]
Abstract
Axons in the adult mammalian central nervous system fail to regenerate after spinal cord injury. Neurons lose their capacity to regenerate during development, but the intracellular processes underlying this loss are unclear. We found that critical components of the presynaptic active zone prevent axon regeneration in adult mice. Transcriptomic analysis combined with live-cell imaging revealed that adult primary sensory neurons downregulate molecular constituents of the synapse as they acquire the ability to rapidly grow their axons. Pharmacogenetic reduction of neuronal excitability stimulated axon regeneration after adult spinal cord injury. Genetic gain- and loss-of-function experiments uncovered that essential synaptic vesicle priming proteins of the presynaptic active zone, but not clostridial-toxin-sensitive VAMP-family SNARE proteins, inhibit axon regeneration. Systemic administration of Baclofen reduced voltage-dependent Ca2+ influx in primary sensory neurons and promoted their regeneration after spinal cord injury. These findings indicate that functional presynaptic active zones constitute a major barrier to axon regeneration.
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Affiliation(s)
- Brett J Hilton
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Andreas Husch
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Barbara Schaffran
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Tien-Chen Lin
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Emily R Burnside
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Sebastian Dupraz
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Max Schelski
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Jisoo Kim
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany; Department of Stem Cell and Regenerative Biology, Center for Brain Science, and Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA
| | | | - Susanne Schoch
- Institute of Neuropathology, Medical Faculty, University of Bonn, 53105 Bonn, Germany
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Frank Bradke
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany.
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Nieuwenhuis B, Eva R. Promoting axon regeneration in the central nervous system by increasing PI3-kinase signaling. Neural Regen Res 2021; 17:1172-1182. [PMID: 34782551 PMCID: PMC8643051 DOI: 10.4103/1673-5374.327324] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Much research has focused on the PI3-kinase and PTEN signaling pathway with the aim to stimulate repair of the injured central nervous system. Axons in the central nervous system fail to regenerate, meaning that injuries or diseases that cause loss of axonal connectivity have life-changing consequences. In 2008, genetic deletion of PTEN was identified as a means of stimulating robust regeneration in the optic nerve. PTEN is a phosphatase that opposes the actions of PI3-kinase, a family of enzymes that function to generate the membrane phospholipid PIP3 from PIP2 (phosphatidylinositol (3,4,5)-trisphosphate from phosphatidylinositol (4,5)-bisphosphate). Deletion of PTEN therefore allows elevated signaling downstream of PI3-kinase, and was initially demonstrated to promote axon regeneration by signaling through mTOR. More recently, additional mechanisms have been identified that contribute to the neuron-intrinsic control of regenerative ability. This review describes neuronal signaling pathways downstream of PI3-kinase and PIP3, and considers them in relation to both developmental and regenerative axon growth. We briefly discuss the key neuron-intrinsic mechanisms that govern regenerative ability, and describe how these are affected by signaling through PI3-kinase. We highlight the recent finding of a developmental decline in the generation of PIP3 as a key reason for regenerative failure, and summarize the studies that target an increase in signaling downstream of PI3-kinase to facilitate regeneration in the adult central nervous system. Finally, we discuss obstacles that remain to be overcome in order to generate a robust strategy for repairing the injured central nervous system through manipulation of PI3-kinase signaling.
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Affiliation(s)
- Bart Nieuwenhuis
- John van Geest Center for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Richard Eva
- John van Geest Center for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
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38
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Mason MRJ, Erp S, Wolzak K, Behrens A, Raivich G, Verhaagen J. The Jun-dependent axon regeneration gene program: Jun promotes regeneration over plasticity. Hum Mol Genet 2021; 31:1242-1262. [PMID: 34718572 PMCID: PMC9029231 DOI: 10.1093/hmg/ddab315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 10/13/2021] [Accepted: 10/25/2021] [Indexed: 11/25/2022] Open
Abstract
The regeneration-associated gene (RAG) expression program is activated in injured peripheral neurons after axotomy and enables long-distance axon re-growth. Over 1000 genes are regulated, and many transcription factors are upregulated or activated as part of this response. However, a detailed picture of how RAG expression is regulated is lacking. In particular, the transcriptional targets and specific functions of the various transcription factors are unclear. Jun was the first-regeneration-associated transcription factor identified and the first shown to be functionally important. Here we fully define the role of Jun in the RAG expression program in regenerating facial motor neurons. At 1, 4 and 14 days after axotomy, Jun upregulates 11, 23 and 44% of the RAG program, respectively. Jun functions relevant to regeneration include cytoskeleton production, metabolic functions and cell activation, and the downregulation of neurotransmission machinery. In silico analysis of promoter regions of Jun targets identifies stronger over-representation of AP1-like sites than CRE-like sites, although CRE sites were also over-represented in regions flanking AP1 sites. Strikingly, in motor neurons lacking Jun, an alternative SRF-dependent gene expression program is initiated after axotomy. The promoters of these newly expressed genes exhibit over-representation of CRE sites in regions near to SRF target sites. This alternative gene expression program includes plasticity-associated transcription factors and leads to an aberrant early increase in synapse density on motor neurons. Jun thus has the important function in the early phase after axotomy of pushing the injured neuron away from a plasticity response and towards a regenerative phenotype.
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Affiliation(s)
- Matthew R J Mason
- Laboratory for Regeneration of Sensorimotor Systems, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Meibergdreef 47, 1105, BA, Amsterdam, The Netherlands
| | - Susan Erp
- Laboratory for Regeneration of Sensorimotor Systems, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Meibergdreef 47, 1105, BA, Amsterdam, The Netherlands
| | - Kim Wolzak
- Laboratory for Regeneration of Sensorimotor Systems, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Meibergdreef 47, 1105, BA, Amsterdam, The Netherlands
| | - Axel Behrens
- Adult Stem Cell Laboratory, The Francis Crick Institute, London, NW1 1AT, United Kingdom
| | - Gennadij Raivich
- UCL Institute for Women's Health, Maternal and Fetal Medicine, Perinatal Brain Repair Group, London, WC1E 6HX, United Kingdom
| | - Joost Verhaagen
- Laboratory for Regeneration of Sensorimotor Systems, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Meibergdreef 47, 1105, BA, Amsterdam, The Netherlands.,Center for Neurogenomics and Cognition Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam, 1081HV, Amsterdam, The Netherlands
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39
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Jang EH, Bae YH, Yang EM, Gim Y, Suh HJ, Kim S, Park SM, Park JB, Hur EM. Comparing axon regeneration in male and female mice after peripheral nerve injury. J Neurosci Res 2021; 99:2874-2887. [PMID: 34510521 DOI: 10.1002/jnr.24955] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Revised: 07/07/2021] [Accepted: 08/17/2021] [Indexed: 02/06/2023]
Abstract
Axons in the adult mammalian central nervous system fail to regenerate after injury. By contrast, spontaneous axon regeneration occurs in the peripheral nervous system (PNS) due to a supportive PNS environment and an increase in the intrinsic growth potential induced by injury via cooperative activation of multifaceted biological pathways. This study compared axon regeneration and injury responses in C57BL/6 male and female mice after sciatic nerve crush (SNC) injury. The extent of axon regeneration in vivo was indistinguishable in male and female mice when observed at 3 days after SNC injury, and primary dorsal root ganglion (DRG) neurons from injured, male and female mice extended axons to a similar length. Moreover, the induction of selected regeneration-associated genes (RAGs), such as Atf3, Sprr1a, Gap43, Sox11, Jun, Gadd45a, and Smad1 were comparable in male and female DRGs when assessed by quantitative real-time reverse transcription polymerase chain reaction. Furthermore, the RNA-seq analysis of male and female DRGs revealed that differentially expressed genes (DEGs) in SNC groups compared to sham-operated groups included many common genes associated with neurite outgrowth. However, we also found that a large number of genes in the DEGs were sex dependent, implicating the involvement of distinct gene regulatory network in the two sexes following peripheral nerve injury. In conclusion, we found that male and female mice mounted a comparable axon regeneration response and many RAGs were commonly induced in response to SNC. However, given that many DEGs were sex-dependently expressed, future studies are needed to investigate whether they contribute to peripheral axon regeneration, and if so, to what extent.
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Affiliation(s)
- Eun-Hae Jang
- Laboratory of Neuroscience, Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul, South Korea
| | - Yun-Hee Bae
- Laboratory of Neuroscience, Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul, South Korea
| | - Eun Mo Yang
- Laboratory of Neuroscience, Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul, South Korea.,BK21 Four Future Veterinary Medicine Leading Education & Research Center, College of Veterinary Medicine, Seoul National University, Seoul, South Korea
| | - Yunho Gim
- Laboratory of Neuroscience, Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul, South Korea
| | - Hyun-Jun Suh
- Laboratory of Neuroscience, Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul, South Korea
| | - Subin Kim
- Laboratory of Neuroscience, Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul, South Korea
| | - Seong-Min Park
- Department of Cancer Biomedical Science, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Republic of Korea
| | - Jong Bae Park
- Department of Cancer Biomedical Science, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Republic of Korea.,Rare Cancer Branch, Research Institute and Hospital, National Cancer Center, Goyang, Republic of Korea
| | - Eun-Mi Hur
- Laboratory of Neuroscience, Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul, South Korea.,BK21 Four Future Veterinary Medicine Leading Education & Research Center, College of Veterinary Medicine, Seoul National University, Seoul, South Korea.,Interdisciplinary Program in Neuroscience, College of Natural Sciences, Seoul National University, Seoul, South Korea
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40
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Aldskogius H, Kozlova EN. Dorsal Root Injury-A Model for Exploring Pathophysiology and Therapeutic Strategies in Spinal Cord Injury. Cells 2021; 10:2185. [PMID: 34571835 PMCID: PMC8470715 DOI: 10.3390/cells10092185] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 08/19/2021] [Accepted: 08/20/2021] [Indexed: 12/12/2022] Open
Abstract
Unraveling the cellular and molecular mechanisms of spinal cord injury is fundamental for our possibility to develop successful therapeutic approaches. These approaches need to address the issues of the emergence of a non-permissive environment for axonal growth in the spinal cord, in combination with a failure of injured neurons to mount an effective regeneration program. Experimental in vivo models are of critical importance for exploring the potential clinical relevance of mechanistic findings and therapeutic innovations. However, the highly complex organization of the spinal cord, comprising multiple types of neurons, which form local neural networks, as well as short and long-ranging ascending or descending pathways, complicates detailed dissection of mechanistic processes, as well as identification/verification of therapeutic targets. Inducing different types of dorsal root injury at specific proximo-distal locations provide opportunities to distinguish key components underlying spinal cord regeneration failure. Crushing or cutting the dorsal root allows detailed analysis of the regeneration program of the sensory neurons, as well as of the glial response at the dorsal root-spinal cord interface without direct trauma to the spinal cord. At the same time, a lesion at this interface creates a localized injury of the spinal cord itself, but with an initial neuronal injury affecting only the axons of dorsal root ganglion neurons, and still a glial cell response closely resembling the one seen after direct spinal cord injury. In this review, we provide examples of previous research on dorsal root injury models and how these models can help future exploration of mechanisms and potential therapies for spinal cord injury repair.
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Affiliation(s)
- Håkan Aldskogius
- Laboratory of Regenertive Neurobiology, Biomedical Center, Department of Neuroscience, Uppsala University, 75124 Uppsala, Sweden;
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41
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Peng Y, Lin H. [Regulatory role of long non-coding RNA in peripheral nerve injury and neural regeneration]. ZHONGGUO XIU FU CHONG JIAN WAI KE ZA ZHI = ZHONGGUO XIUFU CHONGJIAN WAIKE ZAZHI = CHINESE JOURNAL OF REPARATIVE AND RECONSTRUCTIVE SURGERY 2021; 35:1051-1056. [PMID: 34387437 DOI: 10.7507/1002-1892.202103107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Objective To summarize the regulatory role of long non-coding RNA (lncRNA) in peripheral nerve injury (PNI) and neural regeneration. Methods The characteristics and mechanisms of lncRNA were summarized and its regulatory role in PNI and neural regeneration were elaborated by referring to relevant domestic and foreign literature in recent years. Results Neuropathic pain and denervated muscle atrophy are common complications of PNI, affecting patients' quality of life. Numerous lncRNAs are upregulated after PNI, which promote the progress of neuropathic pain by regulating nerve excitability and neuroinflammation. Several lncRNAs are found to promote the progress of denervated muscle atrophy. Importantly, peripheral nerve regeneration occurs after PNI. LncRNAs promote peripheral nerve regeneration through promoting neuronal axonal outgrowth and the proliferation and migration of Schwann cells. Conclusion At present, the research on lncRNA regulating PNI and neural regeneration is still in its infancy. The specific mechanism remains to be further explored. How to achieve clinical translation of experimental results is also a major challenge for future research.
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Affiliation(s)
- Ying Peng
- Trauma Clinic Medicine Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 201600, P.R.China
| | - Haodong Lin
- Trauma Clinic Medicine Center, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 201600, P.R.China
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42
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MicroRNAs 21 and 199a-3p Regulate Axon Growth Potential through Modulation of Pten and mTor mRNAs. eNeuro 2021; 8:ENEURO.0155-21.2021. [PMID: 34326064 PMCID: PMC8362682 DOI: 10.1523/eneuro.0155-21.2021] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 07/11/2021] [Accepted: 07/15/2021] [Indexed: 12/14/2022] Open
Abstract
Increased mTOR activity has been shown to enhance regeneration of injured axons by increasing neuronal protein synthesis, while PTEN signaling can block mTOR activity to attenuate protein synthesis. MicroRNAs (miRs) have been implicated in regulation of PTEN and mTOR expression, and previous work in spinal cord showed an increase in miR-199a-3p after spinal cord injury (SCI) and increase in miR-21 in SCI animals that had undergone exercise. Pten mRNA is a target for miR-21 and miR-199a-3p is predicted to target mTor mRNA. Here, we show that miR-21 and miR-199a-3p are expressed in adult dorsal root ganglion (DRG) neurons, and we used culture preparations to test functions of the rat miRs in adult DRG and embryonic cortical neurons. miR-21 increases and miR-199a-3p decreases in DRG neurons after in vivo axotomy. In both the adult DRG and embryonic cortical neurons, miR-21 promotes and miR-199a-3p attenuates neurite growth. miR-21 directly bound to Pten mRNA and miR-21 overexpression decreased Pten mRNA levels. Conversely, miR-199a-3p directly bound to mTor mRNA and miR-199a-3p overexpression decreased mTor mRNA levels. Overexpressing miR-21 increased both overall and intra-axonal protein synthesis in cultured DRGs, while miR-199a-3p overexpression decreased this protein synthesis. The axon growth phenotypes seen with miR-21 and miR-199a-3p overexpression were reversed by co-transfecting PTEN and mTOR cDNA expression constructs with the predicted 3′ untranslated region (UTR) miR target sequences deleted. Taken together, these studies indicate that injury-induced alterations in miR-21 and miR-199a-3p expression can alter axon growth capacity by changing overall and intra-axonal protein synthesis through regulation of the PTEN/mTOR pathway.
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Alhajlah S, Thompson AM, Ahmed Z. Overexpression of Reticulon 3 Enhances CNS Axon Regeneration and Functional Recovery after Traumatic Injury. Cells 2021; 10:2015. [PMID: 34440784 PMCID: PMC8395006 DOI: 10.3390/cells10082015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 08/03/2021] [Accepted: 08/05/2021] [Indexed: 11/29/2022] Open
Abstract
CNS neurons are generally incapable of regenerating their axons after injury due to several intrinsic and extrinsic factors, including the presence of axon growth inhibitory molecules. One such potent inhibitor of CNS axon regeneration is Reticulon (RTN) 4 or Nogo-A. Here, we focused on RTN3 as its contribution to CNS axon regeneration is currently unknown. We found that RTN3 expression correlated with an axon regenerative phenotype in dorsal root ganglion neurons (DRGN) after injury to the dorsal columns, a well-characterised model of spinal cord injury. Overexpression of RTN3 promoted disinhibited DRGN neurite outgrowth in vitro and dorsal column axon regeneration/sprouting and electrophysiological, sensory and locomotor functional recovery after injury in vivo. Knockdown of protrudin, however, ablated RTN3-enhanced neurite outgrowth/axon regeneration in vitro and in vivo. Moreover, overexpression of RTN3 in a second model of CNS injury, the optic nerve crush injury model, enhanced retinal ganglion cell (RGC) survival, disinhibited neurite outgrowth in vitro and survival and axon regeneration in vivo, an effect that was also dependent on protrudin. These results demonstrate that RTN3 enhances neurite outgrowth/axon regeneration in a protrudin-dependent manner after both spinal cord and optic nerve injury.
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Affiliation(s)
- Sharif Alhajlah
- Neuroscience and Ophthalmology, Institute of Inflammation and Ageing, University of Birmingham, Birmingham B15 2TT, UK; (S.A.); (A.M.T.)
- Applied Medical Science College, Shaqra University, P.O. Box 1678, Ad-Dawadmi 11911, Saudi Arabia
| | - Adam M Thompson
- Neuroscience and Ophthalmology, Institute of Inflammation and Ageing, University of Birmingham, Birmingham B15 2TT, UK; (S.A.); (A.M.T.)
| | - Zubair Ahmed
- Neuroscience and Ophthalmology, Institute of Inflammation and Ageing, University of Birmingham, Birmingham B15 2TT, UK; (S.A.); (A.M.T.)
- Centre for Trauma Sciences Research, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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Dubový P, Hradilová-Svíženská I, Brázda V, Joukal M. Toll-Like Receptor 9-Mediated Neuronal Innate Immune Reaction Is Associated with Initiating a Pro-Regenerative State in Neurons of the Dorsal Root Ganglia Non-Associated with Sciatic Nerve Lesion. Int J Mol Sci 2021; 22:ijms22147446. [PMID: 34299065 PMCID: PMC8304752 DOI: 10.3390/ijms22147446] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 07/07/2021] [Accepted: 07/08/2021] [Indexed: 12/27/2022] Open
Abstract
One of the changes brought about by Wallerian degeneration distal to nerve injury is disintegration of axonal mitochondria and consequent leakage of mitochondrial DNA (mtDNA)—the natural ligand for the toll-like receptor 9 (TLR9). RT-PCR and immunohistochemical or Western blot analyses were used to detect TLR9 mRNA and protein respectively in the lumbar (L4-L5) and cervical (C7-C8) dorsal root ganglia (DRG) ipsilateral and contralateral to a sterile unilateral sciatic nerve compression or transection. The unilateral sciatic nerve lesions led to bilateral increases in levels of both TLR9 mRNA and protein not only in the lumbar but also in the remote cervical DRG compared with naive or sham-operated controls. This upregulation of TLR9 was linked to activation of the Nuclear Factor kappa B (NFκB) and nuclear translocation of the Signal Transducer and Activator of Transcription 3 (STAT3), implying innate neuronal immune reaction and a pro-regenerative state in uninjured primary sensory neurons of the cervical DRG. The relationship of TLR9 to the induction of a pro-regenerative state in the cervical DRG neurons was confirmed by the shorter lengths of regenerated axons distal to ulnar nerve crush following a previous sciatic nerve lesion and intrathecal chloroquine injection compared with control rats. The results suggest that a systemic innate immune reaction not only triggers the regenerative state of axotomized DRG neurons but also induces a pro-regenerative state further along the neural axis after unilateral nerve injury.
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EFA6 in Axon Regeneration, as a Microtubule Regulator and as a Guanine Nucleotide Exchange Factor. Cells 2021; 10:cells10061325. [PMID: 34073530 PMCID: PMC8226579 DOI: 10.3390/cells10061325] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/23/2021] [Accepted: 05/24/2021] [Indexed: 11/17/2022] Open
Abstract
Axon regeneration after injury is a conserved biological process that involves a large number of molecular pathways, including rapid calcium influx at injury sites, retrograde injury signaling, epigenetic transition, transcriptional reprogramming, polarized transport, and cytoskeleton reorganization. Despite the numerous efforts devoted to understanding the underlying cellular and molecular mechanisms of axon regeneration, the search continues for effective target molecules for improving axon regeneration. Although there have been significant historical efforts towards characterizing pro-regenerative factors involved in axon regeneration, the pursuit of intrinsic inhibitors is relatively recent. EFA6 (exchange factor for ARF6) has been demonstrated to inhibit axon regeneration in different organisms. EFA6 inhibition could be a promising therapeutic strategy to promote axon regeneration and functional recovery after axon injury. This review summarizes the inhibitory role on axon regeneration through regulating microtubule dynamics and through affecting ARF6 (ADP-ribosylation factor 6) GTPase-mediated integrin transport.
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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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Zhang S, Liu B, Zhu H, Jin H, Gong Z, Qiu H, Xu M, Chen M, Nan K, Wu W. A Novel Rat Model with Long Range Optic Nerve Injury to Study Retinal Ganglion Cells Endogenous Regeneration. Neuroscience 2021; 465:71-84. [PMID: 33895340 DOI: 10.1016/j.neuroscience.2021.04.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 03/26/2021] [Accepted: 04/15/2021] [Indexed: 10/21/2022]
Abstract
In adult mammals, axon regeneration is limited within the lesion site after injury to the optic nerve. Changes in the microenvironment of lesion sites play an important role in retinal ganglion cells (RGCs) axon regeneration along with other intrinsic factors. In this study, the effect of the lesion site on the microenvironment and axon growth was evaluated using a refined optic nerve crush (ONC) injury model, in which the injury range was extended compared to classical injury. The number of regenerated axons labeled anterogradely with cholera toxin B fragment (CTB) was significantly increased in the long-range crush injury (LI) group compared to the ONC group at distances of 500, 1000 and 1500 µm from the initial site of the injury. These data confirmed that RGC axons can regenerate inside the lesion site. Immunofluorescence and proteomic analysis showed that the microenvironment at the lesion site was highly heterogeneous. The levels of myelin-associated inhibitors, chondroitin-sulfate proteoglycans (CSPGs) and other axon growth inhibitors decreased inside the lesion site compared to the posterior segment of the optic nerve lesion site. The expression of multiple lysosome-related enzymes, metabolic inhibitors including cholesterol esterase, cathepsin B, D, Z and arylsulfatase B (ARSB) were significantly increased inside the lesion site for the LI group compared to the normal optic nerves. Our results suggest that the model of long range optic nerve injury is more useful towards understanding the lesion microenvironment and the endogenous regeneration of RGCs. Also, we showed that myelin and neurocan (a CSPG) are differently expressed in the optic nerve between the interior and posterior lesion sites and may explain why axons cannot reach the brain through the lesion site.
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Affiliation(s)
- Si Zhang
- The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou 325027, China
| | - Bo Liu
- The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou 325027, China
| | - Hui Zhu
- The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou 325027, China
| | - Haochen Jin
- The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou 325027, China
| | - Zan Gong
- The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou 325027, China
| | - Haijun Qiu
- The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou 325027, China
| | - Mingna Xu
- The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou 325027, China
| | - Mei Chen
- Department of Ophthalmology, Dazhou Central Hospital, Dazhou, Sichuan 635000, China
| | - Kaihui Nan
- The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou 325027, China.
| | - Wencan Wu
- The Eye Hospital, School of Ophthalmology & Optometry, Wenzhou Medical University, Wenzhou 325027, China.
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Shahsavani N, Kataria H, Karimi-Abdolrezaee S. Mechanisms and repair strategies for white matter degeneration in CNS injury and diseases. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166117. [PMID: 33667627 DOI: 10.1016/j.bbadis.2021.166117] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/22/2021] [Accepted: 02/23/2021] [Indexed: 12/14/2022]
Abstract
White matter degeneration is an important pathophysiological event of the central nervous system that is collectively characterized by demyelination, oligodendrocyte loss, axonal degeneration and parenchymal changes that can result in sensory, motor, autonomic and cognitive impairments. White matter degeneration can occur due to a variety of causes including trauma, neurotoxic exposure, insufficient blood flow, neuroinflammation, and developmental and inherited neuropathies. Regardless of the etiology, the degeneration processes share similar pathologic features. In recent years, a plethora of cellular and molecular mechanisms have been identified for axon and oligodendrocyte degeneration including oxidative damage, calcium overload, neuroinflammatory events, activation of proteases, depletion of adenosine triphosphate and energy supply. Extensive efforts have been also made to develop neuroprotective and neuroregenerative approaches for white matter repair. However, less progress has been achieved in this area mainly due to the complexity and multifactorial nature of the degeneration processes. Here, we will provide a timely review on the current understanding of the cellular and molecular mechanisms of white matter degeneration and will also discuss recent pharmacological and cellular therapeutic approaches for white matter protection as well as axonal regeneration, oligodendrogenesis and remyelination.
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Affiliation(s)
- Narjes Shahsavani
- Department of Physiology and Pathophysiology, Regenerative Medicine Program, Spinal Cord Research Centre, Children's Hospital Research Institute of Manitoba, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Hardeep Kataria
- Department of Physiology and Pathophysiology, Regenerative Medicine Program, Spinal Cord Research Centre, Children's Hospital Research Institute of Manitoba, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Soheila Karimi-Abdolrezaee
- Department of Physiology and Pathophysiology, Regenerative Medicine Program, Spinal Cord Research Centre, Children's Hospital Research Institute of Manitoba, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada.
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Liu C, Liu J, Liu C, Zhou Q, Zhou Y, Zhang B, Saijilafu. The intrinsic axon regenerative properties of mature neurons after injury. Acta Biochim Biophys Sin (Shanghai) 2021; 53:1-9. [PMID: 33258872 DOI: 10.1093/abbs/gmaa148] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Indexed: 01/07/2023] Open
Abstract
Thousands of nerve injuries occur in the world each year. Axon regeneration is a very critical process for the restoration of the injured nervous system's function. However, the precise molecular mechanism or signaling cascades that control axon regeneration are not clearly understood, especially in mammals. Therefore, there is almost no ideal treatment method to repair the nervous system's injury until now. Mammalian axonal regeneration requires multiple signaling pathways to coordinately regulate gene expression in soma and assembly of the cytoskeleton protein in the growth cone. A better understanding of their molecular mechanisms, such as axon regeneration regulatory signaling cascades, will be helpful in developing new treatment strategies for promoting axon regeneration. In this review, we mainly focus on describing these regeneration-associated signaling cascades, which regulate axon regeneration.
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Affiliation(s)
- Chunfeng Liu
- Department of Orthopedic Surgery, Suzhou Kowloon Hospital, Shanghai Jiaotong University Medical School, Suzhou 215000, China
| | - Jinlian Liu
- Department of Orthopedic Surgery, Suzhou Kowloon Hospital, Shanghai Jiaotong University Medical School, Suzhou 215000, China
| | - Chaoqun Liu
- Department of Orthopedic Surgery, Suzhou Kowloon Hospital, Shanghai Jiaotong University Medical School, Suzhou 215000, China
| | - Qing Zhou
- Department of Orthopedic Surgery, Suzhou Kowloon Hospital, Shanghai Jiaotong University Medical School, Suzhou 215000, China
| | - Yaodong Zhou
- Department of Orthopedic Surgery, Suzhou Kowloon Hospital, Shanghai Jiaotong University Medical School, Suzhou 215000, China
| | - Boyin Zhang
- Orthopedics Surgery Department, China-Japan Union Hospital of Jilin University, Changchun 130033, China
| | - Saijilafu
- Department of Orthopaedics, The First Affiliated Hospital, Orthopaedic Institute, Soochow University, Suzhou 215007, China
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Ewan EE, Avraham O, Carlin D, Gonçalves TM, Zhao G, Cavalli V. Ascending dorsal column sensory neurons respond to spinal cord injury and downregulate genes related to lipid metabolism. Sci Rep 2021; 11:374. [PMID: 33431991 PMCID: PMC7801468 DOI: 10.1038/s41598-020-79624-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 12/07/2020] [Indexed: 02/08/2023] Open
Abstract
Regeneration failure after spinal cord injury (SCI) results in part from the lack of a pro-regenerative response in injured neurons, but the response to SCI has not been examined specifically in injured sensory neurons. Using RNA sequencing of dorsal root ganglion, we determined that thoracic SCI elicits a transcriptional response distinct from sciatic nerve injury (SNI). Both SNI and SCI induced upregulation of ATF3 and Jun, yet this response failed to promote growth in sensory neurons after SCI. RNA sequencing of purified sensory neurons one and three days after injury revealed that unlike SNI, the SCI response is not sustained. Both SCI and SNI elicited the expression of ATF3 target genes, with very little overlap between conditions. Pathway analysis of differentially expressed ATF3 target genes revealed that fatty acid biosynthesis and terpenoid backbone synthesis were downregulated after SCI but not SNI. Pharmacologic inhibition of fatty acid synthase, the enzyme generating palmitic acid, decreased axon growth and regeneration in vitro. These results support the notion that decreased expression of lipid metabolism-related genes after SCI, including fatty acid synthase, may restrict axon regenerative capacity after SCI.
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Affiliation(s)
- Eric E Ewan
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Oshri Avraham
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Dan Carlin
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Tassia Mangetti Gonçalves
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Guoyan Zhao
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA
| | - Valeria Cavalli
- Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8108, St. Louis, MO, 63110-1093, USA. .,Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Center of Regenerative Medicine, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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