scholarly journals Chronic neuronal activation increases dynamic microtubules to enhance functional axon regeneration after dorsal root crush injury

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Di Wu ◽  
Ying Jin ◽  
Tatiana M. Shapiro ◽  
Abhishek Hinduja ◽  
Peter W. Baas ◽  
...  
Keyword(s):  
Dorsal Root ◽  
Axon Regeneration ◽  
Axon Growth ◽  
Crush Injury ◽  
Neuronal Activation ◽  
Drg Neurons ◽  
Root Entry Zone ◽  
The Status

AbstractAfter a dorsal root crush injury, centrally-projecting sensory axons fail to regenerate across the dorsal root entry zone (DREZ) to extend into the spinal cord. We find that chemogenetic activation of adult dorsal root ganglion (DRG) neurons improves axon growth on an in vitro model of the inhibitory environment after injury. Moreover, repeated bouts of daily chemogenetic activation of adult DRG neurons for 12 weeks post-crush in vivo enhances axon regeneration across a chondroitinase-digested DREZ into spinal gray matter, where the regenerating axons form functional synapses and mediate behavioral recovery in a sensorimotor task. Neuronal activation-mediated axon extension is dependent upon changes in the status of tubulin post-translational modifications indicative of highly dynamic microtubules (as opposed to stable microtubules) within the distal axon, illuminating a novel mechanism underlying stimulation-mediated axon growth. We have identified an effective combinatory strategy to promote functionally-relevant axon regeneration of adult neurons into the CNS after injury.

scholarly journals Injury-free priming: induction of Primary Afferent Collateral Sprouting in uninjured sensory neurons in vivo primes them for enhanced axon outgrowth in vitro

2018 ◽  
Author(s):  
Sara Soleman ◽  
Jeffrey C. Petruska ◽  
Lawrence D.F. Moon
Keyword(s):  
Axon Regeneration ◽  
Axonal Injury ◽  
Axon Growth ◽  
Drg Neurons ◽  
Primary Afferent ◽  
Collateral Sprouting ◽  
Axon Elongation ◽  
Defined Media

AbstractPrior “conditioning” nerve lesions can prime DRG neurons for enhanced axon regeneration. Here, we tested the hypothesis that adult DRG neurons can be primed for axon elongation in vitro without axonal injury by prior induction of Primary Afferent Collateral Sprouting (PACS) in vivo. Thoracic cutaneous nerves (T9, T10, T12, T13 but not T11) were transected to create zones of denervated skin. Neurons from the uninjured T11 DRG underwent PACS within the skin, as demonstrated by the expansion of its zones responsive to pinch up to 14 days. At 7 or 14 days after induction of collateral sprouting, DRG neurons were dissociated and cultured for 18 hours in defined media lacking neurotrophins and growth factors. Neurons from the uninjured T11 DRG had longer mean neurite lengths than neurons from naïve DRG. A larger proportion of neurons from the uninjured T11 DRG showed an elongating or arborizing phenotype than neurons from naïve DRG. Transcriptomic analysis of the uninjured T11 DRG and denervated/reinnervated skin reveal regulation of receptor/ligand systems and regulators of growth during collateral sprouting. For example, the glial cell-derived neurotrophic family ligands Artemin and Persephin were upregulated in denervated skin after 7 and/or 14 days. We suggest that extracellular cues in denervated skin modify the intrinsic growth program of uninjured DRG neurons that enhances their ability to elongate or arborize even after explantation. Collectively, these data confirm that induction of collateral sprouting does not induce an injury response yet primes many of these uninjured neurons for in vitro axon growth.

Similar Electrophysiological Changes in Axotomized and Neighboring Intact Dorsal Root Ganglion Neurons

2003 ◽  
Vol 89 (3) ◽  
pp. 1588-1602 ◽  
Author(s):  
Chao Ma ◽  
Yousheng Shu ◽  
Zheng Zheng ◽  
Yong Chen ◽  
Hang Yao ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Receptive Fields ◽  
Input Resistance ◽  
Spinal Nerve ◽  
Dorsal Root Ganglion Neurons ◽  
Drg Neurons ◽  
Ganglion Neurons

We investigated electrophysiological changes in chronically axotomized and neighboring intact dorsal root ganglion (DRG) neurons in rats after either a peripheral axotomy consisting of an L5 spinal nerve ligation (SNL) or a central axotomy produced by an L5 partial rhizotomy (PR). SNL produced lasting hyperalgesia to punctate indentation and tactile allodynia to innocuous stroking of the foot ipsilateral to the injury. PR produced ipsilateral hyperalgesia without allodynia with recovery by day 10. Intracellular recordings were obtained in vivo from the cell bodies (somata) of axotomized and intact DRG neurons, some with functionally identified peripheral receptive fields. PR produced only minor electrophysiological changes in both axotomized and intact somata in L5 DRG. In contrast, extensive changes were observed after SNL in large- and medium-sized, but not small-sized, somata of intact (L4) as well as axotomized (L5) DRG neurons. These changes included (in relation to sham values) higher input resistance, lower current and voltage thresholds, and action potentials with longer durations and slower rising and falling rates. The incidence of spontaneous activity, recorded extracellularly from dorsal root fibers in vitro, was significantly higher (in relation to sham) after SNL but not after PR, and occurred in myelinated but not unmyelinated fibers from both L4 (9.1%) and L5 (16.7%) DRGs. We hypothesize that the changes in the electrophysiological properties of axotomized and intact DRG neurons after SNL are produced by a mechanism associated with Wallerian degeneration and that the hyperexcitability of intact neurons may contribute to SNL-induced hyperalgesia and allodynia.

scholarly journals Estrogen Elicits Dorsal Root Ganglion Axon Sprouting via a Renin-Angiotensin System

Endocrinology ◽  
2008 ◽  
Vol 149 (7) ◽  
pp. 3452-3460 ◽  
Author(s):  
Anuradha Chakrabarty ◽  
Audrey Blacklock ◽  
Stanislav Svojanovsky ◽  
Peter G. Smith
Keyword(s):  
Estrogen Receptor ◽  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Drg Neurons ◽  
Predisposing Factor ◽  
Adult Rats ◽  
Axon Sprouting ◽  
Pain Syndromes

Many painful conditions occur more frequently in women, and estrogen is a predisposing factor. Estrogen may contribute to some pain syndromes by enhancing axon outgrowth by sensory dorsal root ganglion (DRG) neurons. The objective of the present study was to define mechanisms by which estrogen elicits axon sprouting. The estrogen receptor-α agonist propyl pyrazole triol induced neurite outgrowth from cultured neonatal DRG neurons, whereas the estrogen receptor-β agonist diarylpropionitrile was ineffective. 17β-Estradiol (E2) elicited sprouting from peripherin-positive unmyelinated neurons, but not larger NF200-positive myelinated neurons. Microarray analysis showed that E2 up-regulates angiotensin II (ANGII) receptor type 2 (AT2) mRNA in vitro, and studies in adult rats confirmed increased DRG mRNA and protein in vivo. AT2 plays a central role in E2-induced axon sprouting because AT2 blockade by PD123,319 eliminated estrogen-mediated sprouting in vitro. We assessed whether AT2 may be responding to locally synthesized ANGII. DRG from adult rats expressed mRNA for renin, angiotensinogen, and angiotensin converting enzyme (ACE), and protein products were present and occasionally colocalized within neurons and other DRG cells. We determined if locally synthesized ANGII plays a role in estrogen-mediated sprouting by blocking its formation using the ACE inhibitor enalapril. ACE inhibition prevented estrogen-induced neuritogenesis. These findings support the hypothesis that estrogen promotes DRG nociceptor axon sprouting by up-regulating the AT2 receptor, and that locally synthesized ANGII can induce axon formation. Therefore, estrogen may contribute to some pain syndromes by enhancing the pro-neuritogenic effects of AT2 activation by ANGII.

scholarly journals Integrin-driven Axon Regeneration in the Spinal Cord Activates a Distinctive CNS Regeneration Program

2021 ◽  
Author(s):  
Menghon Cheah ◽  
Yuyan Cheng ◽  
Veselina Petrova ◽  
Anda Cimpean ◽  
Pavla Jendelova ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Sensory Neurons ◽  
Axonal Regeneration ◽  
Dorsal Root ◽  
Axon Regeneration ◽  
Peripheral Nerve Regeneration ◽  
Axon Growth ◽  
Drg Neurons ◽  
Cns Regeneration ◽  
Sensory Axons

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 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 and caused expression of a distinctive CNS regeneration program, including genes associated with ubiquitination, autophagy, endoplasmic reticulum, trafficking, and signalling. Pharmacological inhibition of these processes blocked the regeneration of axons from DRGs and human iPS-derived sensory neurons, validating their causal contributions. 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, Tfeb, Yy1. Signalling from integrins primes sensory neurons for regeneration, but their axon growth in the CNS is associated with a distinctive program that differs from that involved in PNS regeneration.

scholarly journals Oncomodulin derived from regeneration-associated macrophages in dorsal root ganglia promotes axon regeneration in the spinal cord

2021 ◽  
Author(s):  
Min Kwon ◽  
Yeojin Seo ◽  
Hana Cho ◽  
Jihye Choi ◽  
Hyung Soon Kim ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Neurite Outgrowth ◽  
Dorsal Root Ganglia ◽  
Axonal Regeneration ◽  
Dorsal Root ◽  
Axon Regeneration ◽  
Signal Sequence ◽  
Drg Neurons ◽  
Cord Injury

Preconditioning peripheral nerve injury enhances axonal regeneration of dorsal root ganglia (DRG) neurons in part by driving pro-regenerative perineuronal macrophage activation. How these regeneration-associated macrophages influence the neuronal capacity of axon regeneration remains elusive. The present study reports that oncomodulin (ONCM) is an effector molecule derived from the regeneration-associated macrophages. ONCM was highly upregulated in DRG macrophages following preconditioning injury and necessary for the preconditioning-induced neurite outgrowth. ONCM-deficient macrophages failed to generate neurite outgrowth activity of the conditioned medium in the in vitro model of neuron-macrophage interaction. CCL2/CCR2 signaling is an upstream regulator of ONCM since the ONCM upregulation was dependent on CCR2 and CCL2 overexpression-mediated conditioning effects were attenuated in ONCM-deficient mice. Direct application of ONCM potently increased neurite outgrowth in cultured DRG neurons by activating a distinct gene set, particularly neuropeptide-related genes. AAV-mediated overexpression of ONCM construct with the signal sequence increased neuronal secretion of ONCM and enhanced neurite outgrowth in an autocrine manner. For a clinically relevant approach, we developed a nanogel-mediated system for localized delivery of recombinant ONCM to DRG tissue. Electrostatic encapsulation of ONCM by a reducible epsilon-poly(L-lysine)-nanogel (REPL-NG) resulted in a slow release of ONCM allowing sustained bioactivity. Intraganglionic injection of REPL-NG/ONCM complex achieved a remarkable long-range axonal regeneration beyond spinal cord lesion, surpassing the extent expected from the preconditioning effects. The NG-mediated ONCM delivery could be exploited as a therapeutic strategy for promoting sensory axon regeneration following spinal cord injury.

scholarly journals Intra-articular AAV-PHP.S mediated chemogenetic targeting of knee-innervating dorsal root ganglion neurons alleviates inflammatory pain in mice

2020 ◽  
Author(s):  
Sampurna Chakrabarti ◽  
Luke A. Pattison ◽  
Balint Doleschall ◽  
Rebecca H. Rickman ◽  
Helen Blake ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Knee Joint ◽  
Joint Pain ◽  
Dorsal Root ◽  
Dorsal Root Ganglion Neurons ◽  
Drg Neurons ◽  
Neuron Excitability ◽  
Ganglion Neurons

AbstractObjectiveJoint pain is the major clinical symptom of arthritis that affects millions of people. Controlling the excitability of knee-innervating dorsal root ganglion (DRG) neurons (knee neurons) could potentially provide pain relief. Therefore, our objective was to evaluate whether the newly engineered adeno-associated virus (AAV) serotype, AAV-PHP.S, can deliver functional artificial receptors to control knee neuron excitability following intra-articular knee injection.MethodsAAV-PHP.S virus packaged with dTomato fluorescent protein and either excitatory (Gq) or inhibitory (Gi) designer receptors activated by designer drugs (DREADDs) was injected into the knee joint of adult mice. Labelling of DRG neurons by AAV-PHP.S from the knee was evaluated using immunohistochemistry. Functionality of Gq- and Gi-DREADDs was evaluated using whole-cell patch clamp electrophysiology on acutely cultured DRG neurons. Pain behavior in mice was assessed using a digging assay, dynamic weight bearing and rotarod, before and after intra-peritoneal administration of the DREADD activator, Compound 21.ResultsWe show that AAV-PHP.S can deliver functional genes into the DRG neurons when injected into the knee joint in a similar manner to the well-established retrograde tracer, fast blue. Short-term activation of AAV-PHP.S delivered Gq-DREADD increases excitability of knee neurons in vitro, without inducing overt pain in mice when activated in vivo. By contrast, in vivo Gi-DREADD activation alleviated complete Freund’s adjuvant mediated knee inflammation-induced deficits in digging behavior, with a concomitant decrease in knee neuron excitability observed in vitro.ConclusionsWe describe an AAV-mediated chemogenetic approach to specifically control joint pain, which may be utilized in translational arthritic pain research.

scholarly journals N6-methyladenine DNA demethylase ALKBH1 regulates mammalian axon regeneration

2020 ◽  
Author(s):  
Qiao Li ◽  
Cheng Qian ◽  
Harry Feng ◽  
Tyger Lin ◽  
Ying Huang ◽  
...  
Keyword(s):  
Sensory Neurons ◽  
Neuronal Development ◽  
Axon Regeneration ◽  
Physiological Function ◽  
Axon Growth ◽  
Epigenetic Mechanism ◽  
Sensory Axon ◽  
Functional Roles

AbstractRecent studies have shown that DNA N6-methyladenine (N6-mA) modification is emerging to be a novel and important epigenetic regulator of mammalian gene transcription. Several studies demonstrated DNA N6-mA in human or rodents was regulated by methyltransferase N6AMT1 and demethylase ALKBH1. Moreover, studies in mouse brain or human glioblastoma cells showed that reduced level of N6-mA or higher level of ALKBH1 was correlated with up regulated levels of genes associated with neuronal development. We thus investigated the functional roles of ALKBH1 in sensory axon regeneration. Our results showed that ALKBH1 regulated the level of N6-mA in sensory neurons, and upon peripheral nerve injury ALKBH1 was up regulated in mouse sensory neurons. Functionally, knocking down ALKBH1 in sensory neurons resulted in reduced axon regeneration in vitro and in vivo, which could be rescued by simultaneously knocking down N6AMT1. Moreover, knocking down ALKBH1 led to decreased levels of many neurodevelopment regulatory genes, including neuritin that is well known to enhance axon growth and regeneration. Our study not only revealed a novel physiological function of DNA N6-mA, but also identified a new epigenetic mechanism regulating mammalian axon regeneration.Significance StatementThe study demonstrated that DNA N6-methyladenine (N6-mA) modification played important roles in regulation of sensory axon regeneration, likely through controlling the expression of neurodevelopmental associated genes. The results will add new evidence about the physiological function of DNA N6-mA and its regulatory demethylase ALKBH1 in neurons.

scholarly journals Overexpression of Reticulon 3 enhances CNS axon regeneration and functional recovery after injury

2021 ◽  
Author(s):  
Zubair Ahmed ◽  
Sharif Alhajlah ◽  
Adam Thompson
Keyword(s):  
Spinal Cord ◽  
Optic Nerve ◽  
Neurite Outgrowth ◽  
Functional Recovery ◽  
Axon Regeneration ◽  
Axon Growth ◽  
Dorsal Root Ganglion Neurons ◽  
Ganglion Neurons

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-66. Here, we focused on RTN3 as its contribution in 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 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.

scholarly journals Thiamine Suppresses Thermal Hyperalgesia, Inhibits Hyperexcitability, and Lessens Alterations of Sodium Currents in Injured, Dorsal Root Ganglion Neurons in Rats

2009 ◽  
Vol 110 (2) ◽  
pp. 387-400 ◽  
Author(s):  
Xue-Song Song ◽  
Zhi-Jiang Huang ◽  
Xue-Jun Song
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Root Ganglion ◽  
Nerve Injury ◽  
Dorsal Root ◽  
Thermal Hyperalgesia ◽  
B Vitamins ◽  
Drg Neurons ◽  
Na Currents

Background B vitamins can effectively attenuate inflammatory and neuropathic pain in experimental animals, while their efficacy in treating clinical pain syndromes remains unclear. To understand possible mechanisms underlying B vitamin-induced analgesia and provide further evidence that may support the clinical utility of B vitamins in chronic pain treatment, this study investigated effects of thiamine (B1) on the excitability and Na currents of dorsal root ganglion (DRG) neurons that have been altered by nerve injury. Methods Nerve injury was mimicked by chronic compression of DRG in rats. Neuropathic pain was evidenced by the presence of thermal hyperalgesia. Intracellular and patch-clamp recordings were made in vitro from intact and dissociated DRG neurons, respectively. Results (1) In vivo intraperitoneal administration of B1 (66 mg/kg/day, 10-14 doses) significantly inhibited DRG compression-induced neural hyperexcitability, in addition to suppressing thermal hyperalgesia. (2) In vitro perfusion of B1 (0.1, 1 and 10 mM) resulted in a dose-dependent inhibition of DRG neuron hyperexcitability. In addition, the DRG neurons exhibited size-dependent sensitivity to B1 treatment, i.e., the small and the medium-sized neurons, compared to the large neurons, were significantly more sensitive. (3) Both in vitro (1 mM) and in vivo application of B1 significantly reversed DRG compression-induced down-regulation of tetrodotoxin-resistant but not tetrodotoxin-sensitive Na current density in the small neurons. B1 at 1 mM also reversed the compression-induced hyperpolarizing shift of the inactivation curve of the tetrodotoxin-resistant currents and the upregulated ramp currents in small DRG neurons. Conclusion Thiamine can reduce hyperexcitability and lessen alterations of Na currents in injured DRG neurons, in addition to suppressing thermal hyperalgesia.

scholarly journals Overexpression of Reticulon 3 Enhances CNS Axon Regeneration and Functional Recovery after Traumatic Injury

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 2015
Author(s):  
Sharif Alhajlah ◽  
Adam M Thompson ◽  
Zubair Ahmed
Keyword(s):  
Spinal Cord ◽  
Optic Nerve ◽  
Neurite Outgrowth ◽  
Functional Recovery ◽  
Axon Regeneration ◽  
Axon Growth ◽  
Dorsal Root Ganglion Neurons ◽  
Ganglion Neurons

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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