Project description:This program addresses the gene signature associated with DRG in the Chung rat model for neuropathic pain. The Chung neuropathic pain profiling data was analyzed by identifying genes that were up- and down-regulated at selected p value and fold change in DRG of the Sprague Dawley rats following spinal nerve ligation compared to the sham-operated controls.
Project description:Neuropathic pain is a prevalent and debilitating chronic disease that is characterized by activation in glial cells in various pain-related regions within the central nervous system. Recent studies have suggested a sexually dimorphic role of microglia in the maintenance of neuropathic pain in rodents. Here, we utilized RNA sequencing analysis of microglia to identify whether there is a common neuropathic microglial signature and characterize the sex differences in microglia in pain-related regions in nerve injury and chemotherapy-induced peripheral neuropathy mouse models. Whilst mechanical allodynia and behavioral changes were observed in all models, transcriptomic analysis of microglia revealed no common transcriptional changes in spinal and supraspinal regions and in different neuropathic models. However, there was a substantial change in microglial gene expression within the ipsilateral lumbar spinal cord 7-days after chronic constriction injury (CCI) of the sciatic nerve. Both sexes upregulated genes associated with inflammation, phagosome, and lysosome activation, though males revealed a prominent global transcriptional shift not observed in female mice. This study demonstrates a lack of a common neuropathic microglial signature and indicates distinct sex differences in spinal microglia, suggesting they contribute to the sex-specific pain processing following nerve injury.
Project description:Spinal microglia play a pivotal role in the development of neuropathic pain. Peripheral nerve injury induces changes in the transcriptional profile of microglia, including increased expression of components of translational machinery. Whether microglial protein synthesis is stimulated following nerve injury and has a functional role in mediating pain hypersensitivity is unknown. Here, we show that nascent protein synthesis is upregulated in spinal microglia following peripheral nerve injury. Stimulating mRNA translation in microglia, via selective ablation of the translational repressor, eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), promoted the transition of microglia to a reactive state and induced mechanical hypersensitivity. Conversely, inhibiting microglial translation by expressing mutant 4E-BP1 in microglia attenuated their peripheral nerve injury-induced activation and alleviated neuropathic pain. Thus, the stimulation of 4E-BP1-dependent translation promotes microglia reactivity and mechanical hypersensitivity, whereas its inhibition alleviates neuropathic pain.
Project description:Expression profiling of L4 and L5 Dorsal Root Ganglion (DRG) in the spinal nerve ligation model of neuropathic pain. The goal of the study was to identify genes involved in neuropathic pain
Project description:Histone deacetylase inhibitors (HDACIs) interfere with the epigenetic process of histone acetylation and are known to have analgesic properties in models of chronic inflammatory pain. The aim of this study was to determine whether these compounds could also affect neuropathic pain. Different class I HDACIs were delivered intrathecally into rat spinal cord in models of traumatic nerve injury and antiretroviral drug-induced peripheral neuropathy (stavudine, d4T). Mechanical and thermal hypersensitivity was attenuated by 40% to 50% as a result of HDACI treatment, but only if started before any insult. The drugs globally increased histone acetylation in the spinal cord, but appeared to have no measurable effects in relevant dorsal root ganglia in this treatment paradigm, suggesting that any potential mechanism should be sought in the central nervous system. Microarray analysis of dorsal cord RNA revealed the signature of the specific compound used (MS-275) and suggested that its main effect was mediated through HDAC1. Taken together, these data support a role for histone acetylation in the emergence of neuropathic pain. n = 4, HDACi treated vs. vehicle treated. Injured ipsilateral DRG after L5 spinal nerve transection. Spinal cord tissue was run in a separate Affymetrix experiment.
Project description:Histone deacetylase inhibitors (HDACIs) interfere with the epigenetic process of histone acetylation and are known to have analgesic properties in models of chronic inflammatory pain. The aim of this study was to determine whether these compounds could also affect neuropathic pain. Different class I HDACIs were delivered intrathecally into rat spinal cord in models of traumatic nerve injury and antiretroviral drug-induced peripheral neuropathy (stavudine, d4T). Mechanical and thermal hypersensitivity was attenuated by 40% to 50% as a result of HDACI treatment, but only if started before any insult. The drugs globally increased histone acetylation in the spinal cord, but appeared to have no measurable effects in relevant dorsal root ganglia in this treatment paradigm, suggesting that any potential mechanism should be sought in the central nervous system. Microarray analysis of dorsal cord RNA revealed the signature of the specific compound used (MS-275) and suggested that its main effect was mediated through HDAC1. Taken together, these data support a role for histone acetylation in the emergence of neuropathic pain. n = 4, HDACi treated vs. vehicle treated. Ipsilateral dorsal spinal cord tissue after L5 spinal nerve transection, DRG tissue was run in a separate Affymetrix experiment.
Project description:Two out-bred rat selection lines were separated to produce different hypersensitivity phenotypes following nerve injury. These lines were termed High Pain and Low Pain (HP or LP). Each sub-strain was either subject to a Sham surgery or a Spinal Nerve Ligation (SNL) surgery to the L4 and L5 spinal nerves. Three days following surgery L4/L5 Dorsal Root Ganglia (DRG) were dissected from these animals. For the rat line separation protocol see: Devor M, Raber P (1990) Heritability of symptoms in an experimental model of neuropathic pain. Pain 42:51-67. 12 Hybridizations, 3 per condition; Sham HP DRG; 3 day SNL HP DRG; Sham LP DRG; 3 day SNL LP DRG.
Project description:Microglia in the spinal dorsal horn have been implicated in the pathogenesis of neuropathic pain following peripheral nerve injury. We have revently found that CD11c-expressing spinal microglia appear after the development of behavioral pain hypersensitivity following nerve injury and are essential for recovery from neuropathic pain. In order to better understand the gene expression profiles of CD11c-expressing microglia, we performed quantitative bulk RNA sequencing of microglia isolated from mice expressing Venus fluorescent protein under the control of CD11c promoter. We found that CD11c-expressing microglia show distinct gene expression profile compared to CD11c-negative microglia following nerve injury.
Project description:Expression profiling of L4 and L5 Dorsal Root Ganglion (DRG) in the spinal nerve ligation model of neuropathic pain. The goal of the study was to identify genes involved in neuropathic pain This series of samples comprises of contralateral and ipsilateral L4 and L5 DRG tissue collected 4 weeks after rats underwent a L5 spinal nerve ligation (SNL) or a sham operation with no L5 spinal nerve ligation. This defines 8 groups (i) contralateral L4 DRG from the sham cohort (n=5), (ii) ipsilateral L4 DRG from sham cohort (n=5), (iii) contralateral L4 DRG from SNL cohort (n=5), (iv) ipsilateral L4 DRG from the SNL chort (n=5), (v) contralateral L5 DRG from the sham cohort (n=5), (vi) ipsilateral L5 DRG from sham cohort (n=5), (vii) contralateral L5 DRG from SNL cohort (n=5), (viii) ipsilateral L5 DRG from the SNL cohort (n=5)
Project description:Neuropathic pain is an apparently spontaneous experience triggered by abnormal physiology of the peripheral or central nervous system, which evolves with time. Neuropathic pain arising from peripheral nerve injury is characterized by a combination of spontaneous pain, hyperalgesia and allodynia. There is no evidence of this type of pain in human infants or rat pups; brachial plexus avulsion, which causes intense neuropathic pain in adults, is not painful when the injury is sustained at birth. Since infants are capable of nociception from before birth and display both acute and chronic inflammatory pain behaviour from an early neonatal age, it appears that the mechanisms underlying neuropathic pain are differentially regulated over a prolonged postnatal period. We used microarrays to detail the global programme of gene expression underlying the differences in nerve injury between along the postnatal development and identified distinct classes of regulated genes during the injury Experiment Overall Design: We have performed a microarray analysis of the rat L4/L5 dorsal root ganglia, 7 days post spared nerve injury, a model of neuropathic pain. Genes that are regulated in adult rats displaying neuropathic behaviour were compared to those regulated in young rats (10 days old) that did not show the same neuropathic behaviour.