Atopic Dermatitis Samples Research Articles

RNA-sequencing of paired tape-strips and skin biopsies in atopic dermatitis reveals key differences.

Skin tape-strips and biopsies are widely used methods for investigating the skin in atopic dermatitis (AD). Biopsies are more commonly used but can cause scarring and pain, whereas tape-strips are noninvasive but sample less tissue. The study evaluated the performance of skin tape-strips and biopsies for studying AD. Whole-transcriptome RNA-sequencing was performed on paired tape-strips and biopsies collected from lesional and non-lesional skin from AD patients (n = 7) and non-AD controls (n = 5). RNA yield, mapping efficiency, and differentially expressed genes (DEGs) for the two methods (tape-strip/biopsy) and presence of AD (AD/non-AD) were compared. Tape-strips demonstrated a lower RNA yield (22 vs. 4596 ng) and mapping efficiency to known genes (28% vs. 93%) than biopsies. Gene-expression profiles of paired tape-strips and biopsies demonstrated a medium correlation (R2 = 0.431). Tape-strips and biopsies demonstrated systematic differences in measured expression levels of 6483 genes across both AD and non-AD samples. Tape-strips preferentially detected many itch (CCL3/CCL4/OSM) and immune-response (CXCL8/IL4/IL5/IL22) genes as well as markers of epidermal dendritic cells (CD1a/CD207), while certain cytokines (IL18/IL37), skin-barrier genes (KRT2/FLG2), and dermal fibroblasts markers (COL1A/COL3A) were preferentially detected by biopsies. Tape-strips identified more DEGs between AD and non-AD (3157 DEGs) then biopsies (44 DEGs). Tape-strips also detected higher levels of bacterial mRNA than biopsies. This study concludes that tape-strips and biopsies each demonstrate respective advantages for measuring gene-expression changes in AD. Thus, the specific skin layers and genes of interest should be considered before selecting either method.

Mapping the immune cell landscape of severe atopic dermatitis by single-cell RNA-seq.

Efforts to profile atopic dermatitis (AD) tissues have intensified, yet comprehensive analysis of systemic immune landscapes in severe AD remains crucial. Employing single-cell RNA sequencing, we analyzed over 300,000 peripheral blood mononuclear cells from 12 severe AD patients (Eczema area and severity index (EASI) > 21) and six healthy controls. Results revealed significant immune cell shifts in AD patients, including increased Th2 cell abundance, reduced NK cell clusters with compromised cytotoxicity, and correlated Type 2 innate lymphoid cell proportions with disease severity. Moreover, unique monocyte clusters reflecting activated innate immunity emerged in very severe AD (EASI > 30). While overall dendritic cells (DCs) counts decreased, a distinct Th2-priming subset termed "Th2_DC" correlated strongly with disease severity, validated across skin tissue data, and flow cytometry with additional independent severe AD samples. Beyond the recognized role of Th2 adaptive immunity, our findings highlight significant innate immune cell alterations in severe AD, implicating their roles in disease pathogenesis and therapeutic potentials. Apart from the widely recognized role of Th2 adaptive immunity in AD pathogenesis, alterations in innate immune cells and impaired cytotoxic cells have also been observed in severe AD. The impact of these alterations on disease pathogenesis and the effectiveness of potential therapeutic targets requires further investigation.

Gene Expression Differences Identified in Skin Samples of Mycosis Fungoides, Atopic Dermatitis, and Psoriasis

Background: Recent advances in the understanding of the molecular mechanisms underlying atopic dermatitis (AD) and psoriasis (PSO) have led to the development of multiple targeted therapies. Yet, molecular heterogeneity contributes to inconsistent clinical presentation and therapeutic response. Further, systemic treatment of presumed AD or PSO can lead to delays in both diagnosis and proper treatment of patients with a true diagnosis of mycosis fungoides (MF) – a potentially dangerous clinical mimic of AD and PSO that requires a rigorous histologic and molecular workup to diagnose. Therefore, a non-invasive method to distinguish molecular profiles of MF from AD and PSO could inform accurate diagnoses and avoid inappropriate treatment of MF. We have previously shown transcriptomic differences in AD and PSO samples obtained by a non-invasive scraping technique. However, this technique has not been used to assess differences in gene expression profiles of MF samples. Objectives: To identify gene expression differences based on diagnosis of MF, AD, or PSO and response to targeted systemic AD or PSO therapies. Methods: Lesional baseline samples were assessed from 76 patients (AD, n=24; PSO, n=48; and MF, n=4) enrolled in one of two IRB-approved studies (IDENTITY or SIGNAL-MF). Lesional samples were collected by epidermal scraping and preserved in RNA buffer. Library preparation and next generation RNA sequencing was performed using the Ion AmpliSeq Transcriptome Human Gene Expression panel on the S5 Prime sequencer (ThermoFisher). Clinical responses for AD and PSO were further assessed over 3 months using the eczema and psoriasis area and severity index (EASI and PASI, respectively). Genes were considered differentially expressed if there was a log2fold change >|1.0| and padj <.05. Results: Statistically significant differences in gene expression were observed between AD, PSO, and MF lesions. Further, genes were differentially expressed in baseline skin scrapings obtained from super-responders to dupilumab, which blocks both IL-4 and IL-13 signaling, and PSO therapies including the IL-23 inhibitor risankizumab relative to those who did not achieve ≥90% improvement. Conclusion: A non-invasive molecular test could be developed to distinguish between AD, PSO, and MF, and further identify super-responders to targeted PSO and AD therapies.

Characterization of the Pro-Inflammatory and Pruritogenic Transcriptome in Skin Lesions of the Experimental Canine Atopic Acute IgE-Mediated Late Phase Reactions Model and Correlation to Acute Skin Lesions of Human Atopic Dermatitis.

Intradermal injection of anti-immunoglobulin E (IgE) antibodies in dogs grossly and histologically resemble naturally occurring atopic dermatitis (AD). However, the activated inflammatory and pruritic pathways have not been characterized. The objectives of this study were to characterize the inflammatory transcriptome of experimental acute canine IgE-induced lesions and to determine how these correlate to the transcriptome of naturally occurring human and canine acute atopic dermatitis. Biopsies were collected at 6 and 24 h after intradermal injections of anticanine-IgE antibodies to eight healthy male castrated Beagles; healthy and saline-injected skin served as controls. We extracted total RNA from skin biopsies and analyzed transcriptome using RNA-sequencing. Gene expressions of IgE-induced biopsies were compared to that of controls from the same subject (1.5-fold change, p-adjusted value ≤ 0.05). Acute IgE-mediated lesions had a significant upregulation of pro-inflammatory (e.g., LTB, IL-1B, PTX3, CCL2, IL6, IL8, IL18), T helper-(Th)1/IFNγ signal (e.g., STAT-1, OASL, MX-1, CXCL10, IL-12A) and Th2 (e.g., IL4R, IL5, IL13, IL33 and POSTN) genes, as well as Th2 chemokines (CCL17, CCL24). Pathway analysis revealed strong significant upregulation of JAK-STAT, histamine, IL-4 and IL13 signaling. Spearman correlation coefficient for the shared DEGs between canine anti-canine-IgE and human AD samples revealed a significant moderate positive correlation for anti-canine-IgE 6-h samples (r = 0.53) and 24-h samples (r = 0.47). In conclusion, acute canine IgE-mediated skin lesions exhibit a multipolar immunological axis upregulation (Th1, Th2 and Th17) in healthy dogs, resembling acute spontaneous human AD lesions.

Association between gene polymorphism of TLR2 and serum level of it in atopic dermatitis in Al-Najaf Governorate, Iraq

The purpose of this study was to investigate the polymorphism of Toll-like receptor 2 (TLR2) in patients with atopic dermatitis using the T-ARMS-PCR technology. The levels of TLR2 in the serum of these patients were then determined using the enzyme-linked immunosorbent test (ELISA). For a period of 16 months, from 1/5/2022 to 1/8/2023, The 100 samples in this study were divided into two groups: the patients (70), whose clinical diagnosis of atopic dermatitis (AD) is confirmed by dermatologists, and the control groups (30), whose immunological and biochemical analyses confirmed their status. Patients and controls were arranged according to age and gender, with age groups further divided into five categories: 1-7, 7-16, 16-33, 33-45, and >45 years, about 70 out of 100 AD samples have TLR2 gene polymorphisms in CC, TT, and TC, and serum TLR2 levels were greater in patients than in controls (p-value=0.029*). In conclusion, atopi dermatitis may be caused by a gene polymorphism in TLR2 in (CC, TT, and TC). Additionally, immunological analysis revealed that AD patients had higher serum levels of TLR2 than did healthy individuals.

Identification of IRF1 as a Novel Pyroptosis-Related Prognostic Biomarker of Atopic Dermatitis.

Purpose: The aim of this study was to characterize key biomarkers associated with pyroptosis in atopic dermatitis (AD). Materials and methods: To identify the differentially expressed pyroptosis-related genes (DEPRGs), the gene expression profiles GSE16161 and GSE32924 from the Gene Expression Omnibus (GEO) database were utilized. Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to determine the potential biological functions and involved pathways. Furthermore, protein-protein interaction network analyses were performed to identify hub genes. The types and proportions of infiltrating immune cells were detected by immune filtration analysis using CIBERSORT. A 12-axis competing endogenous RNA (ceRNA) network was constructed utilizing the miRNet database. Immunohistochemistry (IHC) further validated the differential expression of a key gene IRF1 in the skin tissues collected from AD patients. The collection of skin tissue from human subjects in this study were reviewed and approved by the IRB of Yueyang Integrated Chinese and Western Medicine Hospital (KYSKSB2020-125). Results: The study identified a total of 76 DEPRGs, which were enriched in genes associated with the inflammatory response and immune regulation. There was a higher percentage of activated dendritic cells and a lower percentage of resting mast cells in AD samples. PVT1 expression was associated with upregulation of hub genes including CXCL8, IRF1, MKI67, and TP53 in the ceRNA network and was correlated with activated dendritic cells in AD. As a transcription factor, IRF1 could regulate the production of downstream inflammatory factors. The IHC study revealed that IRF1 was overexpressed in the skin tissues of AD patients, which were consistent with the results of the bioinformatic study. Conclusions: IRF1 and its related genes were identified as key pyroptosis-related biomarkers in AD, which is a crucial pathway in the pathogenesis of AD.

420 Molecular assessment of atopic dermatitis and psoriasis samples collected using a noninvasive technique

Abstract Updates in the molecular understanding of common and often debilitating skin diseases such as atopic dermatitis (AD) and psoriasis led to the development of multiple targeted systemic drugs. Optimal response to these medications relies on correct diagnosis, as well as clinical, personal and molecular factors unique to each patient. Currently, unstandardized assessment of clinical characteristics and comorbidities drive the development of a therapeutic plan for patients with AD and psoriasis. The molecular mechanisms underlying each patient’s disease are not routinely assessed when developing a treatment plan. This empirical approach to treatment selection delays optimal therapeutic response and leads to increased costs to healthcare systems. Therefore, incorporating molecular information from an individual patient’s disease should inform better treatment decisions. Previously, we presented the proof of concept for a noninvasive skin scraping sample collection technique by assessing gene expression differences of select genes of interest from psoriasis and AD samples using quantitative polymerase chain reaction. Indeed, candidate genes were differentially expressed in AD and psoriasis lesions relative to nonlesional skin and in AD relative to psoriasis lesions, demonstrating the feasibility of this collection technique. An algorithm based on the gene expression profiles of AD and psoriasis samples could be used to help guide therapy selection. This study aims to assess the molecular profiles of AD and psoriasis samples collected using a noninvasive skin scraping method with the ultimate goal of developing and validating a molecular test for these common inflammatory skin diseases. The superficial epidermis of lesional and nonlesional skin from patients with AD or psoriasis from three dermatology centers in the USA was collected by gently scraping the skin 10 times with a curette and immediately preserving the sample in a proprietary buffer. RNA isolated from samples was stored at −80°C until further use. Library preparation and next generation RNA sequencing was performed using the Ion AmpliSeq Transcriptome Human Gene Expression panel on the S5XL sequencer (ThermoFisher). Differential expression of genes was assessed using DESeq2; Metascape was used to assess enriched gene ontology of differentially expressed genes. When comparing AD lesional and nonlesional skin, 1633 transcripts were differentially expressed (absolute value of log2fold change >1.0 and padj < 0.05). Additionally, 4468 transcripts were differentially expressed between psoriasis lesional and nonlesional skin. Further, principal component analysis demonstrated that lesional and nonlesional samples for both AD and psoriasis could be distinguished by their respective gene expression profiles. Gene ontology enrichment analysis revealed that innate and adaptive immune system and cytokine signaling genes were among the most common types of differentially expressed genes between lesional and nonlesional samples. Moreover, gene expression differed between lesional AD and psoriasis samples. These results suggest that a molecular test could be developed from AD and psoriasis samples collected by a noninvasive scraping technique. Further, clinical correlation with therapeutic outcomes may be used in conjunction with molecular profiles to develop an algorithm to predict therapeutic response in these common inflammatory skin diseases.

Identification of diagnostic molecules and potential therapeutic agents for atopic dermatitis by single-cell RNA sequencing combined with a systematic computing framework that integrates network pharmacology.

Atopic dermatitis (AD) is composed of highly flexible cellular participants. To better understand its pathobiology and molecular regulation mechanisms, it is necessary to combine single-cell RNA sequencing (scRNA-seq) with new computing frameworks or specific technologies, which may contribute to the development of better treatments for AD. The scRNA-seq data of GSE180885 and bulk RNA-seq data of GSE193309 were obtained from Gene Expression Omnibus (GEO) database, and the scRNA-seq data was analyzed by Seurat package to identify the cell types in AD. The genes related to the activity of AD topical drugs were obtained from the ChEMBL database, which provided a variety of bioactivity data such as multiple drugs and targets. AD-related genes were obtained from DisGeNET and CTD databases synthesizing human disease-related genes; the intersection of AD-related genes from these three sources with differentially expressed genes (DEGs) between non-diseased AD and normal human skin (NHS) samples and differential cell type marker genes was taken. The proximity analysis of drug gene network was performed based on the gene with the largest area of receiver operating characteristic (ROC) curve. Ten distinct cell types of AD and NHS were identified, except for phagocytes cells. Three hub genes, F10 and CALCRL and CTSB, were obtained. The area under the curve of ROC based on CTSB expression was the largest, which was 60.15%. By binding drug CTSB-related gene interaction network, we identified 145 potential drugs. Among them, the score of DB07045 and CTSB docking was the lowest, and molecular docking and molecular dynamics (MD) simulation confirmed the close and stable binding of DB07045 and cathepsin B. This work identified diagnostic molecules and potential therapeutic drugs of AD by scRNA-seq combined with a systematic computing framework of network pharmacology, which may provide valuable clues for drug design.

Increased Serum Levels of Tumor Necrosis Factor-like Ligand 1A in Atopic Dermatitis.

Atopic dermatitis (AD) is a common chronic skin disease with pruritus, affecting 5-20% of the population in developed countries. Though its cause varies from genetic polymorphisms to the environmental factors, the T-helper (Th) 2 inflammation is one of the main characteristic pathoses. TNF superfamily ligand A (TL1A) is a recently discovered cytokine, which is released by various immune cells and reported to have an ability to stimulate Th1, Th2, and Th17 responses. Its association was investigated in chronic inflammatory disease, such as rheumatoid arthritis, inflammatory bowel disease, and psoriasis. However, its role on AD is unclear. To elucidate the association of TL1A in AD, we measured the serum TL1A levels in AD patients and healthy controls and performed the immunohistochemistry of TL1A. The result showed that the serum TL1A levels were higher in AD patients than healthy controls, and they positively correlated with the serum immunoglobulin E levels, serum Lactate dehydrogenase, and the number of eosinophils in peripheral blood. The immunohistochemistry of TL1A also showed TL1A expression in epithelium of AD samples. Because previous studies indicate TL1A has a certain role as an inflammation enhancer in Th2 and/or Th17 polarized disease, TL1A in AD may also has a role as an inflammation generator.

Granzyme K contributes to endothelial microvascular damage and leakage during skin inflammation.

Granzyme K (GzmK) is a serine protease with minimal presence in healthy tissues while abundant in inflamed tissues. Initially thought to play an exclusive role in immune-mediated cell death, extracellular GzmK can also promote inflammation. To evaluate the role of GzmK in the pathogenesis of atopic dermatitis (AD), the most common inflammatory skin disease. A panel of human AD and control samples was analysed to determine if GzmK is elevated. Next, to determine a pathological role for GzmK in AD-like skin inflammation, oxazolone-induced dermatitis was induced in GzmK-/- and wild-type (WT) mice. In human lesional AD samples, there was an increase in the number of GzmK+ cells compared with healthy controls. GzmK-/- mice exhibited reduced overall disease severity characterized by reductions in scaling, erosions and erythema. Surprisingly, the presence of GzmK did not notably increase the overall pro-inflammatory response or epidermal barrier permeability in WT mice; rather, GzmK impaired angiogenesis, increased microvascular damage and microhaemorrhage. Mechanistically, GzmK contributed to vessel damage through cleavage of syndecan-1, a key structural component of the glycocalyx, which coats the luminal surface of vascular endothelia. GzmK may provide a potential therapeutic target for skin conditions associated with persistent inflammation, vasculitis and pathological angiogenesis.

Transient receptor potential vanilloid 3 expression is increased in non-lesional skin of atopic dermatitis patients.

TRPV3 (transient receptor potential vanilloid 3) is a pro‐inflammatory ion channel mostly expressed by keratinocytes of the human skin. Previous studies have shown that the expression of TRPV3 is markedly upregulated in the lesional epidermis of atopic dermatitis (AD) patients suggesting a potential pathogenetic role of the ion channel in the disease. In the current study, we aimed at defining the molecular and functional expression of TRPV3 in non‐lesional skin of AD patients as previous studies implicated that healthy‐appearing skin in AD is markedly distinct from normal skin with respect to terminal differentiation and certain immune function abnormalities. By using multiple, complementary immunolabelling and RT‐qPCR technologies on full‐thickness and epidermal shave biopsy samples from AD patients (lesional, non‐lesional) and healthy volunteers, we provide the first evidence that the expression of TRPV3 is markedly upregulated in non‐lesional human AD epidermis, similar to lesional AD samples. Of further importance, by using the patch‐clamp method on cultured healthy and non‐lesional AD keratinocytes, we also show that this upregulation is functional as determined by the significantly augmented TRPV3‐specific ion current (induced by agonists) on cultured non‐lesional AD keratinocytes when compared to healthy ones.

Transcriptome-based identification of novel endotypes in adult atopic dermatitis.

Atopic dermatitis (AD) is a frequent and heterogeneous inflammatory skin disease, for which personalized medicine remains a challenge. High-throughput approaches have improved understanding of the complex pathophysiology of AD. However, a purely data-driven AD classification is still lacking. To address this question, we applied an original unsupervised approach on the largest available transcriptome dataset of AD lesional (n=82) and healthy (n=213) skin biopsies. Taking into account pathological and physiological state, a variance-based filtering revealed 222 AD-specific hyper-variable genes that efficiently classified the AD samples into 4clusters that turned out to be clinically and biologically distinct. Comparison of gene expressions between clusters identified 3sets of upregulated genes used to derive metagenes (MGs): MG-I (19genes) was associated with IL-1 family signaling (including IL-36A and 36G) and skin remodeling, MG-II (23genes) with negative immune regulation (including IL-34 and 37) and skin architecture, and MG-III (17genes) with B lymphocyte immunity. Sample clusters differed in terms of disease severity (p=.02) and S. aureus (SA) colonization (p=.02). Cluster 1 contained the most severe AD, highest SA colonization, and overexpressed MG-I. Cluster 2 was characterized by less severe AD, low SA colonization, and high MG-II expression. Cluster 3 included mild AD, mild SA colonization, and mild expression of all MGs. Cluster 4had the same clinical features as cluster 3 but had hyper-expression of MG-III. Last, we successfully validated our method and results in an independent cohort. Our study revealed unrecognized AD endotypes with specific underlying biological pathways, highlighting novel pathophysiological mechanisms. These data could provide new insights into personalized treatment strategies.

Increase in primary cilia in the epidermis of patients with atopic dermatitis and psoriasis.

Primary cilia influence cell activity, and thus have a unique role in maintaining cell proliferation and differentiation. In atopic dermatitis (AD) and psoriasis, areas of skin inflammation exhibit dysregulated keratinocyte homeostasis. The role of primary cilia in these conditions remains unclear. The objectives of this study is to elucidate the incidence of primary cilia in skin inflammation and the potential mechanism underlying the dysregulation of keratinocytes. Primary cilia were observed using immunofluorescence staining. Normal skin samples were compared with skin samples from patients with AD or psoriasis in terms of cilia numbers and length. The effect of cytokine stimulation on ciliogenesis in keratinocytes was analysed using a primary keratinocyte culture. IFT88, an important ciliary intraflagellar protein, was blocked in Th2 and Th17 cytokines-stimulated keratinocytes. These effects were analysed with quantitative polymerase chain reaction and Western blot. Significant increases in ciliated cells were observed in AD and psoriasis skin samples compared with normal skin samples. The stimulation of keratinocytes using Th2 and Th17 cytokines modulated the formation of primary cilia. The amount of IFT88 in the primary cilia associated with the phosphorylation of JNK, but not p38, in keratinocytes stimulated with interleukin-13, 17A and 22. An increase of ciliated cells in the epidermis may impair keratinocyte differentiation under stress conditions caused by inflammation in both AD and psoriasis patients.

Bioinformatic analysis of key pathways and genes involved in pediatric atopic dermatitis.

The initiation of atopic dermatitis (AD) typically happens very early in life, but most of our understanding of AD is derived from studies on AD patients in adult. The aim of the present study was to identify gene signature speficic to pediatric AD comapred with adult AD. The gene expression profiles of four datasets (GSE32924, GSE36842, GSE58558, and GSE107361) were downloaded from the GEO database. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were performed, and protein–protein interaction (PPI) network was constructed by Cytoscape software. Total 654 differentially expressed genes (DEGs) (394 up-regulated and 260 down-regulated) were identified in pediatric AD samples with adult AD samples as control. The up-regulated DEGs were significantly enriched in the migration and chemotaxis of granulocyte and neutrophil, while down-regulated DEGs were significantly enriched in biological adhesion. KEGG pathway analysis showed that up-regulated DEGs participated in chemokine signaling pathway while down-regulated DEGs participated in adherens junction, focal adhesion, and regulation of actin cytoskeleton. The top 10 hub genes GAPDH, EGFR, ACTB, ESR1, CDK1, CXCL8, CD44, KRAS, PTGS2, and SMC3 were involved in chemokine signaling pathway, cytokine–cytokine receptor interaction, interleukin-17 signaling pathway, and regulation of actin cytoskeleton. In conclusion, we identified DEGs and hub genes involved in pediatric AD, which might be used as therapeutic targets and diagnostic biomarkers for pediatric AD.

Single-cell transcriptome analysis of human skin identifies novel fibroblast subpopulation and enrichment of immune subsets in atopic dermatitis

Atopic dermatitis (AD) is a prevalent inflammatory skin disease with a complex pathogenesis involving immune cell and epidermal abnormalities. Despite whole tissue biopsy studies that have advanced the mechanistic understanding of AD, single cell-based molecular alterations are largely unknown. Our aims were to construct a detailed, high-resolution atlas of cell populations and assess variability in cell composition and cell-specific gene expression in the skin of patients with AD versus in controls. We performed single-cell RNA sequencing on skin biopsy specimens from 5 patients with AD (4 lesional samples and 5 nonlesional samples) and 7 healthy control subjects, using 10× Genomics. We created transcriptomic profiles for 39,042 AD (lesional and nonlesional) and healthy skin cells. Fibroblasts demonstrated a novel COL6A5+COL18A1+ subpopulation that was unique to lesional AD and expressed CCL2 and CCL19 cytokines. Acorresponding LAMP3+ dendritic cell (DC) population that expressed the CCL19 receptor CCR7 was also unique to AD lesions, illustrating a potential role for fibroblast signaling to immune cells. The lesional AD samples were characterized by expansion of inflammatory DCs (CD1A+FCER1A+) and tissue-resident memory T cells (CD69+CD103+). The frequencies of type 2 (IL13+)/type 22 (IL22+) T cells were higher than those of type 1 (IFNG+) in lesional AD, whereas this ratio was slightly diminished in nonlesional AD and further diminished in controls. AD lesions were characterized by expanded type 2/type 22 T cells and inflammatory DCs, and by a unique inflammatory fibroblast that may interact with immune cells toregulate lymphoid cell organization and type 2 inflammation.

Homeostatic pruning and activity of epidermal nerves are dysregulated in barrier-impaired skin during chronic itch development

The epidermal barrier is thought to protect sensory nerves from overexposure to environmental stimuli, and barrier impairment leads to pathological conditions associated with itch, such as atopic dermatitis (AD). However, it is not known how the epidermal barrier continuously protects nerves for the sensory homeostasis during turnover of the epidermis. Here we show that epidermal nerves are contained underneath keratinocyte tight junctions (TJs) in normal human and mouse skin, but not in human AD samples or mouse models of chronic itch caused by epidermal barrier impairment. By intravital imaging of the mouse skin, we found that epidermal nerve endings were frequently extended and retracted, and occasionally underwent local pruning. Importantly, the epidermal nerve pruning took place rapidly at intersections with newly forming TJs in the normal skin, whereas this process was disturbed during chronic itch development. Furthermore, aberrant Ca2+ increases in epidermal nerves were induced in association with the disturbed pruning. Finally, TRPA1 inhibition suppressed aberrant Ca2+ increases in epidermal nerves and itch. These results suggest that epidermal nerve endings are pruned through interactions with keratinocytes to stay below the TJ barrier, and that disruption of this mechanism may lead to aberrant activation of epidermal nerves and pathological itch.

Analysis of the skin mycobiome in adult patients with atopic dermatitis.

With the recent availability of culture-independent sequencing methods, studies have been conducted to analyse skin micro-organisms present in patients with atopic dermatitis (AD). However, the database on the skin fungal communities, "mycobiome," has been relatively restrictive compared with the bacterial world. We aimed to comparatively analyse the overall skin mycobiome between patients with AD and healthy individuals in the Korean population. We analysed skin swab samples obtained from the antecubital fossae of 8 patients with AD and 8 healthy controls. Using sequencing method followed by direct DNA extraction and molecular PCR, taxonomic compositions of fungi at stepwise level ranks were analysed. The phylogenic marker used was internal transcribed spacer 2 regions of DNA. We observed the tendency of higher intra- and interpersonal taxonomic diversity at genus and species levels in AD samples. Non-Malassezia fungal diversity was also noticeable in the patient group compared with healthy controls. Malassezia globosa and Malassezia restricta were prevalent in all samples across both study groups, and some Malassezia species, including Malassezia sloofiae and Malassezia dermatis, characterized AD. Our data might provide a new insight into the mycobiome of adult AD, which contributes to building a systemic mycobiome database in AD.

Evaluation of intraepidermal nerve fibres in the skin of normal and atopic dogs.

Interest in intraepidermal nerve fibres (IENFs) is rising in human medicine, because variations in fibre density occur in some diseases and these neurites might contribute to disease pathogenesis. An increase in IENF density is seen in human atopic dermatitis (AD); there are no such data in atopic dogs. To compare the prevalence of IENFs in normal and atopic canine skin. Eight millimetre skin punch biopsies were taken from six sites of 25 healthy dogs without dermatitis and compared to lesional and nonlesional skin samples of dogs with AD (23 and 14 dogs, respectively). Thirty micrometre-thick paraffin-embedded sections were stained by indirect immunofluorescence for neuronal beta-3 tubulin. Only sections with detectable dermal nerves were then screened for the presence of IENFs. IENFs were identified in all 25 normal nasal planum sections, but in only one biopsy collected from each of the normal canine haired skin (NCHS) sites. As there was no significant difference in IENF prevalence between NCHS areas, they were grouped together. The rate of detection of IENFs was significantly higher (one-tailed Fisher's test, P = 0.004) in lesional AD specimens (18 of 23; 78%) than in nonlesional AD (four of 14; 29%) and NCHS specimens (four of 111; 4%, P < 0.0001). The prevalence of IENF detection in nonlesional AD samples was significantly higher than in normal canine skin (P = 0.006). IENFs are detected more commonly in canine AD than in normal haired skin; these results are comparable to those seen for human AD.

Th2 cytokines enhance TrkA expression, upregulate proliferation, and downregulate differentiation of keratinocytes

BackgroundNerve growth factor (NGF), a neurotrophin that plays a critical role in developmental neurobiology, is released by proliferating keratinocytes and induces proliferation. ObjectiveThe aim of this study was to investigate the role of tyrosine kinase receptor A (TrkA), a high-affinity receptor of NGF, in human keratinocytes. MethodsExpression of TrkA and NGF in skin diseases was investigated by immunohistochemistry. Expression of TrkA in cells was examined by Western blotting and RT-PCR. Cell proliferation was assessed by BrdU assay. ResultsWe first determined the expression of TrkA and NGF in skin samples from patients with atopic dermatitis, prurigo nodularis, psoriasis vulgaris, and seborrheic keratosis. TrkA was only expressed in proliferating basal cells, and its expression was enhanced in atopic dermatitis samples. NGF expression was enhanced in atopic dermatitis and prurigo nodularis samples and in some samples from seborrheic keratosis patients. Investigation of the role of TrkA in vitro using normal human epidermal keratinocytes (NHEK) revealed that TrkA was significantly enhanced by the T helper type 2 (Th2) cytokines interleukin (IL)-4 and IL-13 but not by other inflammatory cytokines, such as IL-1β, tumor necrosis factor α, interferon γ, or epidermal growth factor. On the other hand, expression of NGF was not altered by Th2 cytokines. Notably, inhibition of TrkA significantly reversed the effects of IL-4 on proliferation and differentiation. Furthermore, overexpression of TrkA enhanced proliferation of NHEK. These results indicate that IL-4-induced TrkA expression in keratinocytes modulates proliferation and differentiation of these cells. ConclusionIncreased TrkA expression in keratinocytes in atopic dermatitis may contribute to the observed epidermal hyperproliferation in these patients.

Distribution of IL-31 and its receptor expressing cells in skin of atopic dermatitis

BackgroundTo understand the clinical segments of IL-31 signaling blockade therapy in pruritus of atopic dermatitis (AD), direct detection of the target proteins in the diseased tissues will provide crucial information. There is a lack of direct evidence concerning the cellular origin of IL-31 in AD skins, and data on the expression of IL-31RA in AD are inconsistent. Also, there is no available information regarding IL-31RA protein expression in human dorsal root ganglia (DRG), which mediates the sensation of itch and is the long-suspected source of the protein. ObjectiveWe sought to obtain direct evidence concerning the distribution of IL-31- and IL-31RA-protein expressing cells and their characteristics in AD skin samples and in human DRG. MethodsIL-31 was detected immunohistochemically in AD skins, and representative sections were double stained with IL-31 and several immune-markers. IL-31RA was stained immunohistochemically in AD skins and normal human DRG, and representative AD skins were double stained with IL-31RA and PGP9.5 (a nerve marker). ResultsIL-31-positive cells were observed as mononuclear infiltrating cells and as CD11b co-expressing cells in severe AD samples. As for IL-31RA, positive reactions were detected in keratinocytes and nerve fibers in the dermis of AD and in the neurons of normal DRG. ConclusionThe detection of IL-31 in infiltrating cells of severe AD skin and of IL-31RA in nerve fibers of AD dermis and normal DRG indicates IL-31 signaling may be a contributing factor in the persistence and exacerbation of AD skin lesions.