Topical gabapentin and its relation to cutaneous innervation in symptomatic lymphocytic primary cicatricial alopecia.

In this pilot study, participants with symptomatic lymphocytic primary cicatricial alopecia applied 6% topical gabapentin solution twice daily to affected areas for 12 weeks. There was a significant reduction in symptoms, but no pronounced effect on nerve fibre density or neuropeptide expression.

Small fiber neuropathy and intractable scalp pruritus in dermatomyositis patients.

Background: Scalp pruritus is a common symptom in Dermatomyositis (DM) patients. There are indications that small nerve fibers neuropathy could be involved in this symptom, however the etiology of scalp pruritus is not fully understood. Objectives: To assess epidermal nerve fiber (ENF) density of dermatomyositis patients with scalp pruritus by biopsy by confocal microscopy and immunohistochemistry with subsequent imaging analysis. Methods: DM patients with severe scalp pruritus from the dermatology outpatient clinic were compared to healthy volunteers. Two 4-mm scalp skin biopsies were obtained above the right ear in the parietal region and below the occipital protuberance in the occipital region. Biopsy specimens were incubated with primary antibodies to protein gene product (PGP 9.5), calcitonin gene-related peptide (CGRP), substance P (SP) were used to visualize nerve fibers (ENF) and collagen IV was used to label the epidermal basement membrane. The number of ENFs per millimeter was counted and recorded as the mean of ± SD of counts in 16 images at two micrometer increments/sections, two from each of the samples. ENF densities were compared between groups and a multiple linear regression model was applied to associated factors with ENF density. Results: Fifteen DM patients with severe scalp pruritus and 12 healthy volunteers were included in the study. The mean number of ENF/mm in occipital region of DM group was 16.0 ± 13.9 while the control group in the same region was 99.8 ± 33.1. In parietal region the number of ENF/mm of DM group was 18.0 ± 20.7 while in control group was 50.4 ± 17.4 (p < 0.001). Conclusion: DM patients with pruritus could have some impairment of small nerve fiber density that could explain their recalcitrant scalp pruritus.

Modifying quantitative sensory testing to investigate behavioral reactivity in a pediatric global developmental delay sample: Relation to peripheral innervation and chronic pain outcomes.

Early tactile and nociceptive (pain) mechanisms in children with global developmental delay at risk for intellectual and developmental disability are not well understood. Sixteen children with global developmental delay (mean age = 5.1 years, SD = 1.4; 50% male) completed a modified quantitative sensory testing (mQST) protocol, an epidermal (skin) punch biopsy procedure, and parent-endorsed measures of pain. Children with reported chronic pain had significantly greater epidermal nerve fiber density (ENFd) compared to children without chronic pain. Based on the mQST trials, ENFd values were associated with increased vocal reactivity overall and specifically during the light touch and cool thermal stimulus trials. The findings support the feasibility of an integrative biobehavioral approach to test nociceptive and tactile peripheral innervation and behavioral reactivity during a standardized sensory test in a high-risk sample for which there is often sensory dysfunction and adaptive behavior impairments.

Glia in Neurodegeneration: The Housekeeper, the Defender and the Perpetrator.

Over the past decade, research has unveiled the intimate relationship between neuroinflammation and neurodegeneration. Microglia and astrocytes react to brain insult by setting up a multimodal inflammatory state and act as the primary defenders and executioners of neuroinflammatory structural and functional changes. Microglia and astrocytes also play critical roles in the maintenance of normal brain function. This intricate balance of homeostatic and neuroinflammatory functions can influence the onset and the course of neurodegenerative diseases. The emergent role of the microglial-astrocytic axis in neurodegenerative disease presents many druggable targets that may have broad therapeutic benefits across neurodegenerative disease. Here, we provide a brief review of the basal function of both microglia and astrocytes, how they are changed in disease states, the significant differences between mouse and human glia, and use of human induced pluripotent stem cells derived from patients to study cell autonomous changes in human astrocytes and microglia.

Global transcriptome analysis of rat dorsal root ganglia to identify molecular pathways involved in incisional pain.

To develop non-opioid therapies for postoperative incisional pain, we must understand its underlying molecular mechanisms. In this study, we assessed global gene expression changes in dorsal root ganglia neurons in a model of incisional pain to identify pertinent molecular pathways. Male, Sprague-Dawley rats underwent infiltration of 1% capsaicin or vehicle into the plantar hind paw (n = 6-9/group) 30 min before plantar incision. Twenty-four hours after incision or sham (control) surgery, lumbar L4-L6 dorsal root ganglias were collected from rats pretreated with vehicle or capsaicin. RNA was isolated and sequenced by next generation sequencing. The genes were then annotated to functional networks using a knowledge-based database, Ingenuity Pathway Analysis. In rats pretreated with vehicle, plantar incision caused robust hyperalgesia, up-regulated 36 genes and downregulated 90 genes in dorsal root ganglias one day after plantar incision. Capsaicin pretreatment attenuated pain behaviors, caused localized denervation of the dermis and epidermis, and prevented the incision-induced changes in 99 of 126 genes. The pathway analyses showed altered gene networks related to increased pro-inflammatory and decreased anti-inflammatory responses in dorsal root ganglias. Insulin-like growth factor signaling was identified as one of the major gene networks involved in the development of incisional pain. Expression of insulin-like growth factor -2 and IGFBP6 in dorsal root ganglia were independently validated with quantitative real-time polymerase chain reaction. We discovered a distinct subset of dorsal root ganglia genes and three key signaling pathways that are altered 24 h after plantar incision but are unchanged when incision was made after capsaicin infiltration in the skin. Further exploration of molecular mechanisms of incisional pain may yield novel therapeutic targets.

Lack of relationship between epidermal denervation by capsaicin and incisional pain behaviours: A laser scanning confocal microscopy study in rats.

BACKGROUND: Spontaneous pain after surgical incision is a significant problem for most post-operative patients. Pain management that relies on opioids is hindered by numerous side effects, fuelling interest in non-opioid alternatives and multimodal approaches. Subcutaneous capsaicin infiltration has shown potential for reducing post-operative pain, but there are unanswered questions about safety and possible side effects. In adult rats, we characterized the analgesic effects of pre-operative capsaicin infiltration into the skin prior to plantar incision and assessed wound healing and epidermal innervation. METHODS: The surgical site on the plantar surface of the rat hind paw was infiltrated with 1% capsaicin or vehicle 30 min or 1 week prior to surgical incision. Spontaneous and evoked pain behaviours were assessed. Digital images of incised hind paws were used to quantify the surface area of the wound after suture removal. Epidermal nerve fibre quantification was performed on peri-incisional tissue biopsies. RESULTS: Intraplantar administration of capsaicin 30 min before surgical incision attenuated spontaneous pain behaviours, heat hyperalgesia, epidermal innervation, but it did not alter the rate of wound healing. Incisional pain hypersensitivity returned to baseline 2 weeks post-incision, at a time when no recovery of epidermal innervation is observed. CONCLUSIONS: Subcutaneous infiltration of capsaicin prior to surgical incision attenuated incision-induced pain behaviours and reduced epidermal innervation around the incision site. The long-lasting epidermal denervation by capsaicin had no impact in the rate of wound healing and recovery from pain behaviours. SIGNIFICANCE: Pre-operative capsaicin infiltration attenuated spontaneous pain-like behaviour and prevented the development of heat hyperalgesia following plantar skin incision. While capsaicin caused long-lasting and widespread loss of epidermal and dermal nerve fibres, there was no measurable impact on the rate of wound healing. Pre- or intra-operative infiltration of capsaicin into surgical sites could act as a safe prophylactic for post-operative pain and reduce the need for opioids during recovery.

Evidence for neurogenic inflammation in lichen planopilaris and frontal fibrosing alopecia pathogenic mechanism.

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) are lymphocytic scarring alopecias affecting primarily the scalp. Although both diseases may share some clinical and histopathological features, in the last decade, FFA has become an "epidemic" particularly in Europe, North and South America with unique clinical manifestations compared to LPP, thus, raising the idea that this disease may have a different pathogenesis. Symptoms such as scalp burning, pruritus or pain are usually present in both diseases, suggesting a possible role for nerves and neuropeptides in the pathogenesis of both diseases. Based on some previous studies, neuropeptides, such as substance P (SP) and calcitonin gene-related peptide (CGRP), have been associated with lipid metabolism and many chronic inflammatory disorders. In this study, we asked if these neuropeptides are associated with LPP and FFA scalp lesions. Alteration in the expression of SP and CGRP in affected and unaffected scalp skin from patients with both diseases was found with examination of sections using immunohistochemical techniques and confocal microscopy. We then quantitatively assessed and compared SP and CGRP expression from control, LPP and FFA scalp biopsies. Although LPP and FFA share similar histopathologic findings, opposite results were found in affected and unaffected scalp in the ELISA tests, suggesting that these diseases may have different pathogenic mechanisms. We also found presence of histopathological inflammation irrespective of evident clinical lesions, which raises the possibility that both diseases may be more generalized processes affecting the scalp.

A clinical case-control comparison of epidermal innervation density in Rett syndrome.

INTRODUCTION: Rett syndrome (RTT), a rare neurodevelopmental disorder occurring primarily in females (1:10-15,000 female live births), is most often caused by loss-of-function mutations in the X-linked methyl-CpG-binding protein 2 gene (MECP2). Clinical observations and preclinical findings indicate apparent abnormal sensory and nociceptive function. There have been no direct investigations of epidermal sensory innervation in patients with RTT. METHODS: We compared 3 mm epidermal punch biopsy specimens from adolescent female RTT patients (N = 4, aged 12-19 years) against an archived approximate age-, sex-, body-site matched comparison sample of healthy adolescent females (N = 8, ages 11-17). RESULTS: Confocal imaging revealed, on average, statistically significant increased epidermal nerve fiber (ENF) peptidergic (co-stained calcitonin gene-related protein [CGRP]) innervation density compared with healthy female control individuals. CONCLUSIONS: Given the clinical phenotype of disrupted sensory function along with diagnostic criteria specific to cold hands/feet and insensitivity to pain, our preliminary observations of ENF peptidergic fiber density differences warrants further investigation of the peripheral neurobiology in RTT.

Comparison of Neurovascular Characteristics of Facial Skin in Patients After Primary and Revision Rhytidectomies.

IMPORTANCE: Wound healing influences both the cosmetic and functional outcomes of facial surgery. Study of cutaneous innervation may afford insight into patients' preoperative wound healing potential and aid in their selection of appropriate surgical procedures. OBJECTIVE: To present the quantitative and qualitative differences of epidermal nerve fibers (ENFs), neurotransmitters, vasculature, and mast cells in facial skin among patients after primary and revision rhytidectomies. DESIGN, SETTING, AND PARTICIPANTS: This pilot study collected cutaneous specimens from 8 female patients aged 42 to 66 years who underwent primary rhytidectomy (n = 5) and revision rhytidectomy (n = 3) at Centennial Lakes Surgery Center, Edina, Minnesota, from July 2010 to March 2014. Tissue was processed for confocal/epifluorescence microscopy and indirect immunofluorescent localization of several neural and tissue antigens as well as basement membrane and mast cell markers. INTERVENTION: Primary rhytidectomy vs revision rhytidectomy with selection of a small area of redundant, otherwise disposed of tissue anterior to the tragus for ENF study. MAIN OUTCOMES AND MEASURES: Demographic characteristics included smoking status; 10-point rating scales for facial sensation, pain, and paresthesias; and confocal/epifluorescence microscopy to quantify ENFs, neurotransmitters, vasculature, and mast cells. RESULTS: Patients in the primary rhytidectomy group had a mean (SD) of 54.4 (31.6) ENFs/mm (range, 14.2-99.2 ENFs/mm), and those in the revision rhytidectomy group had a mean (SD) of 18.6 (5.8) ENFs/mm (range, 13.8-25.0 ENFs/mm). A patient in the primary rhytidectomy group was a 25-pack-year smoker and had 14.2 ENFs/mm, the lowest in both groups. In addition to these structural neural changes, functional neural changes in revision rhytidectomy samples included qualitative changes in normal neural antigen prevalence (substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide). Capillary loops appeared less robust and were less common in dermal papilla among samples from both the primary and revision groups, and mast cells were more degranulated. No differences were found in subjective, self-reported postoperative facial sensation. CONCLUSIONS AND RELEVANCE: Previous skin elevation was associated with decreased epidermal nerve fiber density and qualitative changes in dermal nerves, capillaries, and mast cells in a clinical sample of patients undergoing rhytidectomy. Future research is needed to determine whether histological findings predict wound healing and to better understand the effects of surgery on regenerative capacity of epidermal nerve fibers. LEVEL OF EVIDENCE: NA.

Peripheral Innervation in Children With Global Developmental Delay: Biomarker for Risk for Self-Injurious Behavior?

The relation between somatosensory mechanisms and self-injury among children with neurologic impairments associated with developmental delay is not well understood. We evaluated the feasibility of procuring skin biopsies to examine epidermal nerve fiber density and reported self-injury. Following informed parental consent, epidermal skin biopsies were obtained from a distal leg site with no pre-existing skin damage from 11 children with global developmental delay (55% male; mean age = 36.8 months, 17-63 months). Visual microscopic examination and quantitative analyses showed extremely high epidermal nerve fiber density values for some children. Children with reported self-injury (5/11) had significantly (P < .02) greater density values (138.8, standard deviation = 45.5) than children without self-injury (80.5, standard deviation = 17.5). Results from this novel immunohistologic analysis of skin in very young children with neurodevelopmental delays suggest it may be a useful tool to study peripheral innervation as a possible sensory risk factor for self-injury.

A new mechanism for antiepileptic drug action: vesicular entry may mediate the effects of levetiracetam.

Levetiracetam (LEV) is one of the most commonly prescribed antiepileptic drugs, but its mechanism of action is uncertain. Based on prior information that LEV binds to the vesicular protein synaptic vesicle protein 2A and reduces presynaptic neurotransmitter release, we wanted to more rigorously characterize its effect on transmitter release and explain the requirement for a prolonged incubation period for its full effect to manifest. During whole cell patch recordings from rat hippocampal pyramidal neurons in vitro, we found that LEV decreased synaptic currents in a frequency-dependent manner and reduced the readily releasable pool of vesicles. When we manipulated spontaneous activity and stimulation paradigms, we found that synaptic activity during LEV incubation alters the time at which LEV's effect appears, as well as its magnitude. We believe that synaptic activity and concomitant vesicular release allow LEV to enter recycling vesicles to reach its binding site, synaptic vesicle protein 2A. In support of this hypothesis, a vesicular "load-unload" protocol using hypertonic sucrose in the presence of LEV quickly induced LEV's effect. The effect rapidly disappeared after unloading in the absence of LEV. These findings are compatible with LEV acting at an intravesicular binding site to modulate the release of transmitter and with its most marked effect on rapidly discharging neurons. Our results identify a unique neurobiological explanation for LEV's highly selective antiepileptic effect and suggest that synaptic vesicle proteins might be appropriate targets for the development of other neuroactive drugs.