Leveraging deep single-soma RNA sequencing to explore the neural basis of human somatosensation.

The versatility of somatosensation arises from heterogeneous dorsal root ganglion (DRG) neurons. However, soma transcriptomes of individual human (h)DRG neurons-critical information to decipher their functions-are lacking due to technical difficulties. In this study, we isolated somata from individual hDRG neurons and conducted deep RNA sequencing (RNA-seq) to detect, on average, over 9,000 unique genes per neuron, and we identified 16 neuronal types.

Cutaneous targets for topical pain medications in patients with neuropathic pain: individual differential expression of biomarkers supports the need for personalized medicine.

Introduction: Numerous potential cutaneous targets exist for treating chronic pain with topically applied active pharmaceutical ingredients. This preliminary human skin tissue investigation was undertaken to characterize several key biomarkers in keratinocytes and provide proof-of-principle data to support clinical development of topical compounded formulations for peripheral neuropathic pain syndromes, such as postherpetic neuralgia (PHN).

Objectives: The study intended to identify objective biomarkers in PHN skin on a patient-by-patient personalized medicine platform.

Cutaneous nerve fiber and peripheral Nav1.7 assessment in a large cohort of patients with postherpetic neuralgia.

The mechanisms of pain in postherpetic neuralgia (PHN) are still unclear, with some studies showing loss of cutaneous sensory nerve fibers that seemed to correlate with pain level. We report results of skin biopsies and correlations with baseline pain scores, mechanical hyperalgesia, and the Neuropathic Pain Symptom Inventory (NPSI) in 294 patients who participated in a clinical trial of TV-45070, a topical semiselective sodium 1.7 channel (Nav1.

Single-Soma Deep RNA sequencing of Human DRG Neurons Reveals Novel Molecular and Cellular Mechanisms Underlying Somatosensation.

The versatility of somatosensation arises from heterogeneous dorsal root ganglion (DRG) neurons. However, soma transcriptomes of individual human DRG (hDRG) neurons-critical in-formation to decipher their functions-are lacking due to technical difficulties. Here, we developed a novel approach to isolate individual hDRG neuron somas for deep RNA sequencing (RNA-seq).

Keratinocyte Biomarkers Distinguish Painful Diabetic Peripheral Neuropathy Patients and Correlate With Topical Lidocaine Responsiveness.

This study investigated quantifiable measures of cutaneous innervation and algesic keratinocyte biomarkers to determine correlations with clinical measures of patient pain perception, with the intent to better discriminate between diabetic patients with painful diabetic peripheral neuropathy (PDPN) compared to patients with low-pain diabetic peripheral neuropathy (lpDPN) or healthy control subjects. A secondary objective was to determine if topical treatment with a 5% lidocaine patch resulted in correlative changes among the quantifiable biomarkers and clinical measures of pain perception, indicative of potential PDPN pain relief. This open-label proof-of-principle clinical research study consisted of a pre-treatment skin biopsy, a 4-week topical 5% lidocaine patch treatment regimen for all patients and controls, and a post-treatment skin biopsy.

Specializations of somatosensory innervation in the skin of humpback whales (Megaptera novaeangliae).

Cetacean behavior and life history imply a role for somatosensory detection of critical signals unique to their marine environment. As the sensory anatomy of cetacean glabrous skin has not been fully explored, skin biopsy samples of the flank skin of humpback whales were prepared for general histological and immunohistochemical (IHC) analyses of innervation in this study. Histology revealed an exceptionally thick epidermis interdigitated by numerous, closely spaced long, thin diameter penicillate dermal papillae (PDP).

A peripheral CB2 cannabinoid receptor mechanism suppresses chemotherapy-induced peripheral neuropathy: evidence from a CB2 reporter mouse.

CB2 cannabinoid receptors (CB2) are a promising therapeutic target that lacks unwanted side effects of CB1 activation. However, the cell types expressing CB2 that mediate these effects remain poorly understood. We used transgenic mice with CB2 promoter-driven expression of enhanced green fluorescent protein (EGFP) to study cell types that express CB2 and suppress neuropathic nociception in a mouse model of chemotherapy-induced peripheral neuropathy.

Human-like cutaneous neuropathologies associated with a porcine model of peripheral neuritis: A translational platform for neuropathic pain.

Despite enormous investment in research and development of novel treatments, there remains a lack of predictable, effective, and safe therapeutics for human chronic neuropathic pain (NP) afflictions. NP continues to increase among the population and treatments remain a major unmet public health care need. In recent years, numerous costly (time and money) failures have occurred attempting to translate successful animal pain model results, typically using rodents, to human clinical trials.

The evolution and multi-molecular properties of NF1 cutaneous neurofibromas originating from C-fiber sensory endings and terminal Schwann cells at normal sites of sensory terminations in the skin.

In addition to large plexiform neurofibromas (pNF), NF1 patients are frequently disfigured by cutaneous neurofibromas (cNF) and are often afflicted with chronic pain and itch even from seemingly normal skin areas. Both pNFs and cNF consist primarily of benign hyperproliferating nonmyelinating Schwann cells (nSC). While pNF clearly arise within deep nerves and plexuses, the role of cutaneous innervation in the origin of cNF and in chronic itch and pain is unknown.

Identification of an epidermal keratinocyte AMPA glutamate receptor involved in dermatopathies associated with sensory abnormalities.

Introduction: Epidermal keratinocytes are increasingly recognized as active participants in the sensory transduction of itch and pain, processes known to involve primary afferent glutamatergic neurons. However the role of keratinocyte glutamate signaling in sensory functioning is not fully understood. Here, we present the observation of α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid type glutamate receptors (AMPAR) in epidermal keratinocytes.

Anatomy and immunochemical characterization of the non-arterial peptidergic diffuse dural innervation of the rat and Rhesus monkey: Implications for functional regulation and treatment in migraine.

Objective The interplay between neuronal innervation and other cell types underlies the physiological functions of the dura mater and contributes to pathophysiological conditions such as migraine. We characterized the extensive, but understudied, non-arterial diffuse dural innervation (DDI) of the rat and Rhesus monkey. Methods We used a comprehensive integrated multi-molecular immunofluorescence labeling strategy to extensively profile the rat DDI and to a lesser extent that of the Rhesus monkey.

Fibromyalgia syndrome pathology and environmental influences on afflictions with medically unexplained symptoms.

Fibromyalgia syndrome (FMS) is a clinical disorder predominant in females with unknown etiology and medically unexplained symptoms (MUS), similar to other afflictions, including irritable bowel syndrome (IBS), chronic fatigue syndrome (CFS), post-traumatic stress disorder (PTSD), Gulf War illness (GFI), and others. External environmental stimuli drive behavior and impact physiologic homeostasis (internal environment) via autonomic functioning. These environments directly impact the individual affective state (mind), which feeds back to regulate physiology (body).

CaMKII Controls Whether Touch Is Painful.

Unlabelled: The sensation of touch is initiated when fast conducting low-threshold mechanoreceptors (Aβ-LTMRs) generate impulses at their terminals in the skin. Plasticity in this system is evident in the process of adaption, in which a period of diminished sensitivity follows prior stimulation. CaMKII is an ideal candidate for mediating activity-dependent plasticity in touch because it shifts into an enhanced activation state after neuronal depolarizations and can thereby reflect past firing history.

Elaboration and Innervation of the Vibrissal System in the Rock Hyrax (Procavia capensis).

Mammalian tactile hairs are commonly found on specific, restricted regions of the body, but Florida manatees represent a unique exception, exhibiting follicle-sinus complexes (FSCs, also known as vibrissae or tactile hairs) on their entire body. The orders Sirenia (including manatees and dugongs) and Hyracoidea (hyraxes) are thought to have diverged approximately 60 million years ago, yet hyraxes are among the closest relatives to sirenians. We investigated the possibility that hyraxes, like manatees, are tactile specialists with vibrissae that cover the entire postfacial body.

Sodium channel Nav1.7 in vascular myocytes, endothelium, and innervating axons in human skin.

Background: The skin is a morphologically complex organ that serves multiple complementary functions, including an important role in thermoregulation, which is mediated by a rich vasculature that is innervated by sympathetic and sensory endings. Two autosomal dominant disorders characterized by episodes of severe pain, inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD) have been directly linked to mutations that enhance the function of sodium channel Nav1.7.

Skin Matters: A Review of Topical Treatments for Chronic Pain. Part Two: Treatments and Applications.

In Part One of this two-part series, we discussed skin physiology and anatomy as well as generalities concerning topical analgesics. This modality of therapy has lesser side effects and drug-drug interactions, and patients tolerate this form of therapy better than many oral options. Unfortunately, this modality is not used as often as it could be in chronic pain states, such as that from neuropathic pain.

Skin Matters: A Review of Topical Treatments for Chronic Pain. Part One: Skin Physiology and Delivery Systems.

Chronic pain is a complex disorder with multiple etiologies for which the pathologic mechanisms are still largely unknown, making effective treatment a difficult clinical task. Achieving pain relief along with improved function and quality of life is the primary goal of pain clinicians; however, most patients and healthcare professionals consider 30% pain improvement to be clinically significant-a success level that would be unacceptable in other areas of medicine. Furthermore, patients with chronic pain frequently have multiple comorbidities, including depression and sleep apnea, and most have seen several physicians prior to being seen by a pain specialist, have more than three specific pain generators, and are taking multiple medications.

Nerve growth factor induces sensitization of nociceptors without evidence for increased intraepidermal nerve fiber density.

Nerve growth factor (NGF) is involved in the long-term sensitization of nociceptive processing linked to chronic pain. Functional and structural ("sprouting") changes can contribute. Thus, humans report long-lasting hyperalgesia to mechanical and electrical stimulation after intradermal NGF injection and NGF-induced sprouting has been reported to underlie cancer bone pain and visceral pain.

Natural history of herpes zoster: late follow-up of 3.9 years (n=43) and 7.7 years (n=10).

Postherpetic neuralgia (PHN) is a common complication after herpes zoster (HZ). Subjects who completed a longitudinal observational 6-month study (4 visits) of the natural history of HZ were recontacted for 2 additional follow-up visits that included pain and sensory symptom assessment, quantitative sensory testing, capsaicin response test, and 3-mm punch skin biopsies in HZ-affected, mirror-image, and control skin sites. Forty-three subjects (14 with PHN at 6 months) of the original 94 subjects in the cohort were comprehensively assessed at a median 3.

Excessive peptidergic sensory innervation of cutaneous arteriole-venule shunts (AVS) in the palmar glabrous skin of fibromyalgia patients: implications for widespread deep tissue pain and fatigue.

Objective: To determine if peripheral neuropathology exists among the innervation of cutaneous arterioles and arteriole-venule shunts (AVS) in fibromyalgia (FM) patients.

Setting: Cutaneous arterioles and AVS receive a convergence of vasoconstrictive sympathetic innervation, and vasodilatory small-fiber sensory innervation. Given our previous findings of peripheral pathologies in chronic pain conditions, we hypothesized that this vascular location may be a potential site of pathology and/or serotonergic and norepinephrine reuptake inhibitors (SNRI) drug action.

Air-stimulated ATP release from keratinocytes occurs through connexin hemichannels.

Cutaneous ATP release plays an important role in both epidermal stratification and chronic pain, but little is known about ATP release mechanisms in keratinocytes that comprise the epidermis. In this study, we analyzed ATP release from cultured human neonatal keratinocytes briefly exposed to air, a process previously demonstrated to trigger ATP release from these cells. We show that exposing keratinocytes to air by removing media for 15 seconds causes a robust, long-lasting ATP release.

Understanding chronic inflammatory and neuropathic pain.

This meeting report highlights the main topics presented at the conference "Chronic Inflammatory and Neuropathic Pain," convened jointly by the New York Academy of Sciences, MedImmune, and Grünenthal GmbH, on June 2-3, 2011, with the goal of providing a conducive environment for lively, informed, and synergistic conversation among participants from academia, industry, clinical practice, and government to explore new frontiers in our understanding and treatment of chronic and neuropathic pain. The program included leading and emerging investigators studying the pathophysiological mechanisms underlying neuropathic and chronic pain, and experts in the clinical development of pain therapies. Discussion included novel issues, current challenges, and future directions of basic research in pain and preclinical and clinical development of new therapies for chronic pain.

Dependence on the transcription factor Shox2 for specification of sensory neurons conveying discriminative touch.

Touch sensation is mediated by specific subtypes of sensory neurons which develop in a hierarchical process from common early progenitor neurons, but the molecular mechanism that underlies diversification of touch-sensitive mechanoreceptive neurons is not fully known. Here, we use genetically manipulated mice to examine whether the transcription factor short stature homeobox 2 (Shox2) participates in the acquisition of neuronal subtypes conveying touch sensation. We show that Shox2 encodes the development of category I low-threshold mechanoreceptive neurons in glabrous skin, i.

Keratinocyte expression of calcitonin gene-related peptide β: implications for neuropathic and inflammatory pain mechanisms.

Calcitonin gene-related peptide (CGRP) is a vasodilatory peptide that has been detected at high levels in the skin, blood, and cerebrospinal fluid (CSF) under a variety of inflammatory and chronic pain conditions, presumably derived from peptidergic C and Aδ innervation. Herein, CGRP immunolabeling (IL) was detected in epidermal keratinocytes at levels that were especially high and widespread in the skin of humans from locations afflicted with postherpetic neuralgia (PHN) and complex region pain syndrome type 1 (CRPS), of monkeys infected with simian immunodeficiency virus, and of rats subjected to L5/L6 spinal nerve ligation, sciatic nerve chronic constriction, and subcutaneous injection of complete Freund's adjuvant. Increased CGRP-IL was also detected in epidermal keratinocytes of transgenic mice with keratin-14 promoter driven overexpression of noggin, an antagonist to BMP-4 signaling.