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Interactions between central glial cells and neurons in the pain circuitry are critical contributors to the pathogenesis of chronic pain. In the central nervous system (CNS), two major glial cell types predominate: astrocytes and microglia. Injuries or pathological conditions which evoke pain are concurrently associated with the presence of a reactive microglia or astrocyte state, which is characterized by a variety of changes in the morphological, molecular, and functional properties of these cells. In this review, we highlight the changes that reactive microglia and astrocytes undergo following painful injuries and insults and discuss the critical and interactive role these two cell types play in the initiation and maintenance of chronic pain. Additionally, we focus on several crucial mechanisms by which microglia and astrocytes contribute to chronic pain and provide commentary on the therapeutic promise of targeting these pathways. In particular, we discuss how the inflammasome in activated microglia drives maturation and release of key pro-inflammatory cytokines, which drive pain through neuronal- and glial regulations. Moreover, we highlight several potentially-druggable hemichannels and proteases produced by reactive microglia and astrocytes in pain states and discuss how these pathways regulate distinct phases during pain pathogenesis. We also review two emerging areas in chronic pain research: 1) sexually dimorphic glial cell signaling and 2) the role of oligodendrocytes. Finally, we highlight important considerations for potential pain therapeutics targeting glial cell mediators as well as questions that remain in our conceptual understanding of glial cell activation in pain states.
Learn More >Classification of headache disorders is dependent on a subjective self-report from patients and its interpretation by physicians. We aimed to apply objective data-driven machine learning approaches to analyze patient-reported symptoms and test the feasibility of the automated classification of headache disorders. The self-report data of 2162 patients were analyzed. Headache disorders were merged into five major entities. The patients were divided into training (n = 1286) and test (n = 876) cohorts. We trained a stacked classifier model with four layers of XGBoost classifiers. The first layer classified between migraine and others, the second layer classified between tension-type headache (TTH) and others, and the third layer classified between trigeminal autonomic cephalalgia (TAC) and others, and the fourth layer classified between epicranial and thunderclap headaches. Each layer selected different features from the self-reports by using least absolute shrinkage and selection operator. In the test cohort, our stacked classifier obtained accuracy of 81%, sensitivity of 88%, 69%, 65%, 53%, and 51%, and specificity of 95%, 55%, 46%, 48%, and 51% for migraine, TTH, TAC, epicranial headache, and thunderclap headaches, respectively. We showed that a machine-learning based approach is applicable in analyzing patient-reported questionnaires. Our result could serve as a baseline for future studies in headache research.
Learn More >Migraine has consistently been connected with rosacea. Commonalities in epidemiology, trigger factors and associated neuropeptides support shared aetiology and pathophysiological pathways, though underlying mechanisms remain unclear. We established two cohorts of patients diagnosed with either migraine and/or rosacea. All patients were phenotyped in regard to migraine and rosacea. In this article, we describe the baseline parameters of the cohorts. In the future, we expect that these cohorts will help uncover potential disease overlaps and allow for prolonged follow-up through national Danish health registers.
Learn More >The Headache Disability Inventory assesses the dimensions of headache disability, but it is not available in Brazilian Portuguese yet. We aimed to translate the Headache Disability Inventory into Brazilian Portuguese and analyze its measurement properties.
Learn More >Greater acceptance of chronic pain is associated with lesser levels of pain-related distress and disability and better overall functioning. Pain acceptance is most often assessed using the Chronic Pain Acceptance Questionnaire (CPAQ), which includes both an eight-item short form (CPAQ-8) and a twenty item parent measure (CPAQ-20). This study derived a two-item CPAQ for use in busy clinical settings and for repeated measurement during treatment, the CPAQ-2. An Item Response Theory approach was used to identify the strongest items from the CPAQ-20, one from each of its two subscales. Next, regression analyses were conducted to evaluate the utility of the CPAQ-2 by examining variance accounted for in the CPAQ-8, CPAQ-20, and in measures of depression, pain-related fear, physical disability, and psychosocial disability. Four clinical databases were combined (N = 1776) for the analyses. Items 9 and 14 were identified as the strongest CPAQ-20 items in the IRT analyses. The sum score of these two items accounted for over 60% of the variance in the CPAQ-8 and CPAQ-20. Furthermore, this score accounted for significant variance in measures of depression, pain-related fear, physical disability, and psychosocial disability after controlling for data collection method (i.e., in clinic or online), participant age, education, pain duration, and usual pain. Finally, the amount of variance accounted for by the CPAQ-2 was comparable to that accounted for by both the CPAQ-8 and CPAQ-20. These results provide initial support for the CPAQ-2 and suggest that it is well suited as a brief assessment of chronic pain acceptance.
Learn More >The aim of this systematic review is to indirectly compare the efficacy of any intervention, administered perioperatively, on acute and persistent pain after breast surgery.
Learn More >The recently developed new genome-editing technologies, such as the CRISPR/Cas system, have opened the door for generating genetically modified nonhuman primate (NHP) models for basic neuroscience and brain disorders research. The complex circuit formation and experience-dependent refinement of the human brain are very difficult to model in vitro, and thus require use of in vivo whole-animal models. For many neurodevelopmental and psychiatric disorders, abnormal circuit formation and refinement might be at the center of their pathophysiology. Importantly, many of the critical circuits and regional cell populations implicated in higher human cognitive function and in many psychiatric disorders are not present in lower mammalian brains, while these analogous areas are replicated in NHP brains. Indeed, neuropsychiatric disorders represent a tremendous health and economic burden globally. The emerging field of genetically modified NHP models has the potential to transform our study of higher brain function and dramatically facilitate the development of effective treatment for human brain disorders. In this paper, we discuss the importance of developing such models, the infrastructure and training needed to maximize the impact of such models, and ethical standards required for using these models.
Learn More >Organic electronic devices implemented on flexible thin films are attracting increased attention for biomedical applications because they possess extraordinary conformity to curved surfaces. A neuronal device equipped with an organic light-emitting diode (OLED), used in combination with animals that are genetically engineered to include a light-gated ion channel, would enable cell type-specific stimulation to neurons as well as conformal contact to brain tissue and peripheral soft tissue. This potential application of the OLEDs requires strong luminescence, well over the neuronal excitation threshold in addition to flexibility. Compatibility with neuroimaging techniques such as MRI provides a method to investigate the evoked activities in the whole brain. Here, we developed an ultrathin, flexible, MRI-compatible OLED device and demonstrated the activation of channelrhodopsin-2-expressing neurons in animals. Optical stimulation from the OLED attached to nerve fibers induced contractions in the innervated muscles. Mechanical damage to the tissues was significantly reduced because of the flexibility. Owing to the MRI compatibility, neuronal activities induced by direct optical stimulation of the brain were visualized using MRI. The OLED provides an optical interface for modulating the activity of soft neuronal tissues.
Learn More >Discrimination toward people living with migraine and other headache disorders is widespread and socially accepted. Stigma toward these diseases is both a manifestation of these discriminatory attitudes and a sustainer of them. For those living with migraine and headache disorders, stigma limits the full expression of their lives, as well as the likelihood of receiving health care to reduce the burden. In the past decade, public advocacy organizations have emerged in the United States and internationally to counter the consequences of this stigma. These organizations have raised public awareness of these diseases, corrected misconceptions, and empowered millions of people affected by them. The Alliance for Headache Disorders Advocacy has focused on addressing the structural stigma inherent in discriminatory policies of employers, government agencies, and public institutions. While notable progress has been made, there is considerable work left to be done to increase resources and equity for people living with headache disorders.
Learn More >A substantial fraction of the human population suffers from chronic pain states, which often cannot be sufficiently treated with existing drugs. This calls for alternative targets and strategies for the development of novel analgesics. There is substantial evidence that the G protein-coupled GABA receptor is involved in the processing of pain signals and thus has long been considered a valuable target for the generation of analgesics to treat chronic pain. In this review, the contribution of GABA receptors to the generation and modulation of pain signals, their involvement in chronic pain states as well as their target suitability for the development of novel analgesics is discussed.
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