Side-by-Side Comparison of Skin Biopsies and Skin Tape Stripping Highlights Abnormal Stratum Corneum in Atopic Dermatitis

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Lipase-mediated detoxification of host-derived antimicrobial fatty acids by Staphylococcus aureus

Long-chain fatty acids with antimicrobial properties are abundant on the skin and mucosal surfaces, where they are essential to restrict the proliferation of opportunistic pathogens such as Staphylococcus aureus. These antimicrobial fatty acids (AFAs) elicit bacterial adaptation strategies, which have yet to be fully elucidated. Characterizing the pervasive mechanisms used by S. aureus to resist AFAs could open new avenues to prevent pathogen colonization. Here, we identify the S. aureus lipase Lip2 as a novel resistance factor against AFAs. Lip2 detoxifies AFAs via esterification with cholesterol. This is reminiscent of the activity of the fatty acid-modifying enzyme (FAME), whose identity has remained elusive for over three decades. In vitro, Lip2-dependent AFA-detoxification was apparent during planktonic growth and biofilm formation. Our genomic analysis revealed that prophage-mediated inactivation of Lip2 was rare in blood, nose, and skin strains, suggesting a particularly important role of Lip2 for host - microbe interactions. In a mouse model of S. aureus skin colonization, bacteria were protected from sapienic acid (a human-specific AFA) in a cholesterol- and lipase-dependent manner. These results suggest Lip2 is the long-sought FAME that exquisitely manipulates environmental lipids to promote bacterial growth in otherwise inhospitable niches.

Tape strips detect molecular alterations and cutaneous biomarkers in skin of patients with hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) has a high unmet need for better treatments. Biopsies are considered the gold standard for studying molecular alterations in skin. A reproducible, minimally invasive approach is needed for longitudinal monitoring in trials and in pediatric populations.

OBJECTIVE

To determine whether skin tape strips can detect molecular alterations in HS and identify biomarkers of disease activity.

METHODS

We performed RNA sequencing on tape strips collected from lesional and healthy-appearing (nonlesional) HS skin (n = 22) and healthy controls (n = 21). We correlated the expression of skin biomarkers between tape strips and a previously published gene-signature of HS biopsies.

RESULTS

Tape strips detected upregulation of known HS biomarkers (eg, Interleukin[IL]-17A) in nonlesional and/or lesional skin and also identified novel clinically actionable targets, including OX40 and JAK3. The expression of Th17 and tumor necrosis factor-α pathways were highly correlated between tape strips and biopsies. HS clinical severity was significantly associated with expression of biomarkers (eg tumor necrosis factor-α , IL-17 A/F, OX40, JAK1-3, IL-4R) in HS lesional and/or nonlesional skin.

LIMITATIONS

Sample size. Tape stripping is limited in depth.

CONCLUSION

This study validates tape strips as a minimally-invasive approach to identify cutaneous biomarkers in HS. This provides a novel avenue for monitoring treatment efficacy and a potential step toward individualized therapy in HS.

Tape Stripping - Searching for Minimally Invasive Biomarkers in Atopic Dermatitis

Atopic dermatitis (AD) is nowadays entering a new era of more targeted treatments. However, to make personalized medicine, which we are currently striving for, a reality, a reliable set of validated biomarkers is needed. The most practical seem to be biomarkers that can be obtained easily and minimally invasively. Tape stripping (TS) is a method that provides such an opportunity. This review summarizes the potential biomarkers of AD identified by the minimally invasive TS method. Thymic stromal lymphopoietin (TSLP), interleukin (IL)-13, CC chemokine ligand 17 (CCL17)/thymus and activation-regulated chemokine (TARC) and stratum corneum (SC) lipids can be used as predictive biomarkers for AD occurrence. CCL17/TARC also holds great promise for being reliable biomarkers for AD severity as well as treatment response. Nitric oxide synthase 2 (NOS2)/inducible nitric oxide synthase (iNOS) which high expression is specific for psoriasis may be a good biomarker for differential diagnosis between psoriasis and AD in challenging clinical situations. AD children with food allergy (FA) have a unique endotype characterized by selectively altered expression of various molecules in the skin that can indicate FA coexistence. Unfortunately, although numerous potential biomarkers have been found, none of these candidates have been validated and implemented into routine clinical practice, which still separates us from the possibility of a precise approach to AD patients.

Advancements in Skin-Mediated Drug Delivery: Mechanisms, Techniques, and Applications

Skin-mediated drug delivery methods currently are receiving significant attention as a promising approach for the enhanced delivery of drugs through the skin. Skin-mediated drug delivery offers the potential to overcome the limitations of traditional drug delivery methods, including oral administration and intravenous injection. The challenges associated with drug permeation through layers of skin, which act as a major barrier, are explored, and strategies to overcome these limitations are discussed in detail. This review categorizes skin-mediated drug delivery methods based on the means of increasing drug permeation, and it provides a comprehensive overview of the mechanisms and techniques associated with these methods. In addition, recent advancements in the application of skin-mediated drug delivery are presented. The review also outlines the limitations of ongoing research and suggests future perspectives of studies regarding the skin-mediated delivery of drugs.

Intrapatient comparison of atopic dermatitis skin transcriptome shows differences between tape-strips and biopsies

BACKGROUND

Our knowledge of etiopathogenesis of atopic dermatitis (AD) is largely derived from skin biopsies, which are associated with pain, scarring and infection. In contrast, tape-stripping is a minimally invasive, nonscarring technique to collect skin samples.

METHODS

To construct a global AD skin transcriptomic profile comparing tape-strips to whole-skin biopsies, we performed RNA-seq on tape-strips and biopsies taken from the lesional skin of 20 moderate-to-severe AD patients and the skin of 20 controls. Differentially expressed genes (DEGs) were defined by fold-change (FCH) ≥2.0 and false discovery rate <0.05.

RESULTS

We detected 4104 (2513 Up; 1591 Down) and 1273 (546 Up; 727 Down) DEGs in AD versus controls, in tape-strips and biopsies, respectively. Although both techniques captured dysregulation of key immune genes, tape-strips showed higher FCHs for innate immunity (IL-1B, IL-8), dendritic cell (ITGAX/CD11C, FCER1A), Th2 (IL-13, CCL17, TNFRSF4/OX40), and Th17 (CCL20, CXCL1) products, while biopsies showed higher upregulation of Th22 associated genes (IL-22, S100As) and dermal cytokines (IFN-γ, CCL26). Itch-related genes (IL-31, TRPV3) were preferentially captured by tape-strips. Epidermal barrier abnormalities were detected in both techniques, with terminal differentiation defects (FLG2, PSORS1C2) better represented by tape-strips and epidermal hyperplasia changes (KRT16, MKI67) better detected by biopsies.

CONCLUSIONS

Tape-strips and biopsies capture overlapping but distinct features of the AD molecular signature, suggesting their respective utility for monitoring specific AD-related immune, itch, and barrier abnormalities in clinical trials and longitudinal studies.

Altered Gene Expression of IL-35 and IL-36α in the Skin of Patients with Atopic Dermatitis

A comprehensive understanding of atopic dermatitis (AD) pathogenesis is desired, especially in the current era of novel biologics and small molecule drugs. In recent years, new cytokines have emerged that may play a significant role in the pathogenesis of AD. Using the tape stripping (TS) method, this study analyzed the gene expression of IL-35 and IL-36α in lesional and nonlesional AD skin compared with healthy skin and their association with the clinical features of AD among the Polish population. Ten AD patients and seven healthy individuals were enrolled. The lesional skin of the AD patients showed significantly higher expression levels of IL-35 compared to healthy skin (p = 0.0001). The expression level of IL-36α was significantly higher in lesional AD skin than in nonlesional AD skin (p = 0.0039) and healthy skin (p = 0.0045). There was a significant negative correlation between AD severity and the expression level of IL-35 in both lesional (R = -0.66, p = 0.048) and nonlesional skin (R = -0.9, p = 0.0016). In summary, both IL-35 and IL-36α appear to play a role in the pathogenesis of AD. Furthermore, it might be speculated that IL-35 and IL-36α may be potential candidates for disease biomarkers. However, further studies are needed to verify these assumptions and comprehensively elucidate their importance in the pathogenesis of AD.

A noninvasive method for whole-genome skin methylome profiling

BACKGROUND

Ageing, disease and malignant transformation of the skin are associated with changes in DNA methylation. So far, mostly invasive methodologies such as biopsies have been applied in collecting DNA methylation signatures. Tape stripping offers a noninvasive option for skin diagnostics. It enables the easy but robust capture of biologic material in large numbers of participants without the need for specialized medical personnel.

OBJECTIVES

To design and validate a methodology for noninvasive skin sample collection using tape stripping for subsequent DNA -methylation analysis.

METHODS

A total of 175 participants were recruited and provided tape-stripping samples from a sun-exposed area; 92 provided matched tape-stripping samples from a sun-protected area, and an additional 5 provided matched skin-shave biopsies from the same area. Using -enzymatic conversion and whole-genome Illumina sequencing, we generated genome-wide DNA methylation profiles that were used to evaluate the feasibility of noninvasive data acquisition, to compare with established sampling approaches and to investigate biomarker identification for age and ultraviolet (UV) exposure.

RESULTS

We found that tape-stripping samples showed strong concordance in their global DNA methylation landscapes to those of conventional invasive biopsies. Moreover, we showed sample reproducibility and consistent global methylation profiles in skin tape-stripping samples collected from different areas of the body. Using matched samples from sun-protected and sun-exposed areas of the body we were able to validate the capacity of our method to capture the effects of environmental changes and ageing in a cohort covering various ages, ethnicities and skin types. We found DNA methylation changes on the skin resulting from UV exposure and identified significant age-related hypermethylation of CpG islands, with a pronounced peak effect at 50-55 years of age, including methylation changes in well-described markers of ageing.

CONCLUSIONS

These data demonstrate the feasibility of using tape stripping combined with whole-genome sequencing as a noninvasive approach to measuring DNA methylation changes in the skin. In addition, they outline a viable experimental framework for the use of skin tape stripping, particularly when it is performed in large cohorts of patients to identify biomarkers of skin ageing, UV damage and, possibly, to track treatment response to therapeutic interventions.

Assessment of Treatment-Relevant Immune Biomarkers in Psoriasis and Atopic Dermatitis: Toward Personalized Medicine in Dermatology

Immunologically targeted therapies have revolutionized the treatment of inflammatory dermatoses, including atopic dermatitis and psoriasis. Although immunologic biomarkers hold great promise for personalized classification of skin disease and tailored therapy selection, there are no approved or widely used approaches for this in dermatology. This review summarizes the translational immunologic approaches to measuring treatment-relevant biomarkers in inflammatory skin conditions. Tape strip profiling, microneedle-based biomarker patches, molecular profiling from epidermal curettage, RNA in situ hybridization tissue staining, and single-cell RNA sequencing have been described. We discuss the advantages and limitations of each and open questions for the future of personalized medicine in inflammatory skin disease.

Development of a novel microneedle platform for biomarker assessment of atopic dermatitis patients

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease whose pathogenesis, cause, and treatment have been extensively studied. The association of AD with Th2 cytokines is well known; therefore, the analysis of this association is crucial for the diagnosis and treatment of AD. This study aimed to present a new method for measuring protein biomarkers in patients with AD, before and after treatment, using minimally invasive microneedles.

MATERIALS AND METHODS

First, hyaluronic acid-loaded microneedle patches (HA-MNs) for skin sample collection were fabricated. Next, after Institutional Review Board approval, 20 patients with AD were recruited and skin samples were taken before and after treatment using four different sampling techniques: (1) tape stripping, (2) hydrocolloid patches, (3) hollow microneedles, and (4) HA-MNs. Lastly, proteins were isolated from the collected samples, and AD-related biomarkers were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Proteins were successfully extracted from the skin samples collected by tape stripping, hydrocolloid patches, and HA-MNs, except hollow microneedles. Interleukin (IL)-4, IL-13, and interferon-γ were detected in the HA-MNs only. By comparing the biomarker level correlation before and after treatment and the improvement score of the patients, we observed a significant negative correlation between IL-4 and IL-13 with an improvement in AD symptoms.

CONCLUSION

Overall, our results verified that HA-MNs can be used to effectively analyze protein levels of biomarkers from skin metabolites of patients with AD and can be applied to monitor the treatment progress of patients with AD in a minimally invasive manner.

Skin barrier immunology from early life to adulthood

Our skin has a unique barrier function, which is imperative for the body's protection against external pathogens and environmental insults. Although interacting closely and sharing many similarities with key mucosal barrier sites, such as the gut and the lung, the skin also provides protection for internal tissues and organs and has a distinct lipid and chemical composition. Skin immunity develops over time and is influenced by a multiplicity of different factors, including lifestyle, genetics, and environmental exposures. Alterations in early life skin immune and structural development may have long-term consequences for skin health. In this review, we summarize the current knowledge on cutaneous barrier and immune development from early life to adulthood, with an overview of skin physiology and immune responses. We specifically highlight the influence of the skin microenvironment and other host intrinsic, host extrinsic (e.g. skin microbiome), and environmental factors on early life cutaneous immunity.

Development and validation of a minimally invasive and image-guided tape stripping method to sample atopic skin in children

BACKGROUND

Molecular skin profiling techniques, typically performed on skin samples taken by punch biopsy, have enhanced the understanding of the pathophysiology of atopic dermatitis (AD), thereby enabling the development of novel targeted therapeutics. However, punch biopsies are not always feasible or desirable, and novel minimally invasive methods such as skin tape stripping have been developed.

AIM

To develop, optimize and validate a novel tape stripping method guided by noninvasive in vivo skin imaging to sample atopic skin in children.

METHODS

Skin tape stripping-based procedures were compared and optimized using data from 30 healthy controls (HCs: 5 adults, 25 children) and 39 atopic children. Evaluations were guided by high-resolution photography, reflectance confocal microscopy, optical coherence tomography and transepidermal water loss measurements. We assessed and compared adverse events (AEs), the time needed to perform the sampling and the cDNA levels obtained from the tapes.

RESULTS

Tape stripping methods based on previously described protocols resulted in erosions in all participants and required a median time of 65 min to perform (range 60-70 min), but provided good cDNA yield. Shorter durations appeared less invasive but provided lower cDNA yield. The final optimized tape stripping protocol, using 11 tapes of 22 mm in diameter, each applied twice for 5 s with 90° rotation, did not produce significant AEs, was completed within a median time of 7 min (range 5-15 min) and provided good cDNA yield both in HCs and atopic children.

CONCLUSION

Our minimally invasive method is safe and reliable, and provides reproducible acquisition of cDNA in atopic children. In addition, it enables rapid sample collection, a crucial factor in clinical practice.

Multispectral raster-scanning optoacoustic mesoscopy differentiate lesional from non-lesional atopic dermatitis skin using structural and functional imaging markers

Atopic dermatitis (AD) is a chronic and pruritic skin inflammatory disease causing a significant burden to health care management and patient's quality of life. Seemingly healthy skin or non-lesional sites on AD patients still presents skin barrier defects and immune response, which can develop to AD at a later stage. To investigate further the balance between the epidermal barrier impairment and intrinsic immune dysregulation in AD, we exploited multispectral Raster-Scanning Optoacoustic Mesoscopy (ms-RSOM) to image lesional and non-lesional skin areas on AD patients of different severities non-invasively to elucidate their structural features and functional information. Herein, we demonstrate the objective assessment of AD severity using relative changes in oxygen saturation (δsO₂) levels in microvasculature along with other structural parameters such as relative changes in epidermis thickness (δET) and total blood volume (δTBV) between the lesional and non-lesional areas of the skin. We could observe an increasing trend for δsO₂ and δTBV, which correlated well with the subjective clinical Scoring Atopic Dermatitis (SCORAD) for evaluating the severity. Notably, δET showed a decreasing trend with AD severity, indicating that the difference in epidermal thickness between lesional and non-lesional area of the skin decreases with AD severity. Our results also correlated well with conventional metrics such as trans-epidermal water loss (TEWL) and erythrosine sedimentation rate (ESR). We quantified the δsO₂ and δET changes to objectively evaluate the treatment response before and four months after treatment using topical steroids and cyclosporine in one severe AD patient. We observed reduced δsO₂ and δET post treatment. We envision that in future, functional and structural imaging metrics derived from ms-RSOM can be translated as objective markers to assess and stratify the severity of AD and understand the function of skin barrier dysfunctions and immune dysregulation. It could also be employed to monitor the treatment response of AD in regular clinical settings.

Atopic Dermatitis: Striving for Reliable Biomarkers

Atopic dermatitis (AD) is a highly heterogeneous inflammatory disease regarding both its pathophysiology and clinical manifestations. However, it is treated according to the “one-size-fits-all” approach, which may restrict response to treatment. Thus, there is an unmet need for the stratification of patients with AD into distinct endotypes and clinical phenotypes based on biomarkers that will contribute to the development of precision medicine in AD. The development of reliable biomarkers that may distinguish which patients with AD are most likely to benefit from specific targeted therapies is a complex procedure and to date none of the identified candidate biomarkers for AD has been validated for use in routine clinical practice. Reliable biomarkers in AD are expected to improve diagnosis, evaluate disease severity, predict the course of disease, the development of comorbidities, or the therapeutic response, resulting in effective and personalized treatment of AD. Among the studied AD potential biomarkers, thymus and activation-regulated chemokine/C-C motif ligand 17 (TARC/CCL17) has the greatest evidence-based support for becoming a reliable biomarker in AD correlated with disease severity in both children and adults. In this review, we present the most prominent candidate biomarkers in AD and their suggested use.

The importance of periwound skin in wound healing: an overview of the evidence

DECLARATION OF INTEREST

The authors have no conflicts of interest.

Assessment of biomarkers in pediatric atopic dermatitis by tape strips and skin biopsies

BACKGROUND

The cytokine profile of atopic dermatitis (AD) depends on age, ethnicity, and disease severity. This study examined biomarkers in children with AD collected by tape strips and skin biopsies, and examined whether the levels differed with filaggrin genotype, disease severity, and food allergy.

METHODS

Twenty-five children aged 2-14 years with AD were clinically examined. Skin biopsies were collected from lesional skin and tape strips were collected from lesional and non-lesional skin. We analyzed natural moisturizing factor (NMF) and 17 immune markers represented by mRNA levels in skin biopsies and protein levels in tape strips. Common filaggrin gene mutations were examined in all children.

RESULTS

The cytokine profile in lesional skin was dominated by a T helper (Th) 2 response in skin biopsies, and by a general increase in innate inflammation markers (interleukin (IL)-1α, IL-1β, IL-8, IL-18) along with TARC and CTACK in tape strips. The levels of TARC, CTACK, IL-8, IL-18 showed significant correlation with AD severity in both lesional and non-lesional tape stripped skin, while no significant correlations were observed in skin biopsy data. In tape strips from lesional and non-lesional skin, the levels of NMF and selected cytokines differed significantly between children with and without FLG mutations and food allergy.

CONCLUSION

Sampling of the stratum corneum with non-invasive tape strips can be used to identify biomarkers that are associated with disease severity, food allergy and FLG mutations. Skin biopsies showed robust Th2 signature but was inferior for association analysis regarding severity.

Tape Stripping: Investigational, Diagnostic and Therapeutic Uses in Dermatology

Adhesive tape has been used in the scientific study of human skin for over 90 years. Using the tape stripping method in dermatology has aided in the research and diagnose of different skin diseases. Basic science, identification, and therapeutic interventions in skin diseases such as psoriasis, atopic dermatitis, non-melanoma skin cancer, and melanoma have been studied using this technique. Among many promising applications that will be discussed throughout this paper, the Pigmented Lesion Assay (PLA) will be discussed in depth in relation to melanoma. This product carries considerable and significant research towards early detection of melanoma. Tape stripping is unique and advantageous in its ability to provide a non-surgical approach to evaluating the human epidermis. The cellular and molecular components of the skin are used to diagnose different skin conditions without invasive skin biopsy.

Transcriptomic Profiling of Tape-Strips From Moderate to Severe Atopic Dermatitis Patients Treated With Dupilumab

BACKGROUND

Tape-strips are a minimally invasive approach to characterize skin biomarkers in atopic dermatitis (AD). However, they have not yet been used for tracking gene expression changes with systemic treatment.

OBJECTIVE

The aim of the study was to evaluate gene expression changes and therapeutic response biomarkers in AD patients before and after dupilumab (interleukin 4Rα antibody) treatment using tape-strips to obtain epidermal tissue for analysis.

METHODS

Lesional and nonlesional tape-stripped skin was sampled from 18 AD patients before and after dupilumab treatment and from 17 healthy subjects and analyzed by RNA-seq.

RESULTS

At baseline, we detected 6745 and 4859 differentially expressed genes between lesional and nonlesional skin versus normal, respectively, whereas 841 and 977 genes were differentially expressed after treatment, respectively (fold change >1.5 and false discovery rate <0.05). Tape-strips captured significant modulation with dupilumab in key AD immune (eg, C-C motif chemokine ligand 13 [CCL13], CCL17, CCL18) and barrier (eg, periplakin, FA2H) biomarkers. Changes in biomarkers (CCL20, interleukin 34, FABP7) were also significantly correlated with clinical disease improvements (Eczema Area and Severity Index; R > 0.5 or R < -0.4, P < 0.05).

CONCLUSIONS

This real-life study represents the first comprehensive RNA-seq molecular profiling of tape-strips from moderate to severe AD patients after dupilumab therapy. Analysis of tape strip specimens detected significant gene expression changes in key AD biomarkers with dupilumab treatment, suggesting that this approach may be useful to monitor therapeutic responses in inflammatory skin diseases.

Particulate matter causes skin barrier dysfunction

The molecular mechanisms that underlie the detrimental effects of particulate matter (PM) on skin barrier function are poorly understood. In this study, the effects of PM_2.5 on filaggrin (FLG) and skin barrier function were investigated in vitro and in vivo. The levels of FLG degradation products, including pyrrolidone carboxylic acid, urocanic acid (UCA), and cis/trans-UCA, were significantly decreased in skin tape stripping samples of study subjects when they moved from Denver, an area with low PM_2.5, to Seoul, an area with high PM_2.5 count. Experimentally, PM_2.5 collected in Seoul inhibited FLG, loricrin, keratin-1, desmocollin-1, and corneodesmosin but did not modulate involucrin or claudin-1 in keratinocyte cultures. Moreover, FLG protein expression was inhibited in human skin equivalents and murine skin treated with PM_2.5. We demonstrate that this process was mediated by PM_2.5-induced TNF-α and was aryl hydrocarbon receptor dependent. PM_2.5 exposure compromised skin barrier function, resulting in increased transepidermal water loss, and enhanced the penetration of FITC-dextran in organotypic and mouse skin. PM_2.5-induced TNF-α caused FLG deficiency in the skin and subsequently induced skin barrier dysfunction. Compromised skin barrier due to PM_2.5 exposure may contribute to the development and the exacerbation of allergic diseases such as atopic dermatitis.

RNA tape sampling in cutaneous lupus erythematosus discriminates affected from unaffected and healthy volunteer skin

Objective

Punch biopsy, a standard diagnostic procedure for patients with cutaneous lupus erythematosus (CLE) carries an infection risk, is invasive, uncomfortable and potentially scarring, and impedes patient recruitment in clinical trials. Non-invasive tape sampling is an alternative that could enable serial evaluation of specific lesions. This cross-sectional pilot research study evaluated the use of a non-invasive adhesive tape device to collect messenger RNA (mRNA) from the skin surface of participants with CLE and healthy volunteers (HVs) and investigated its feasibility to detect biologically meaningful differences between samples collected from participants with CLE and samples from HVs.

Methods

Affected and unaffected skin tape samples and simultaneous punch biopsies were collected from 10 participants with CLE. Unaffected skin tape and punch biopsies were collected from 10 HVs. Paired samples were tested using quantitative PCR for a candidate immune gene panel and semi-quantitative immunohistochemistry for hallmark CLE proteins.

Results

mRNA collected using the tape device was of sufficient quality for amplification of 94 candidate immune genes. Among these, we found an interferon (IFN)-dominant gene cluster that differentiated CLE-affected from HV (23-fold change; p<0.001) and CLE-unaffected skin (sevenfold change; p=0.002), respectively. We found a CLE-associated gene cluster that differentiated CLE-affected from HV (fourfold change; p=0.005) and CLE-unaffected skin (fourfold change; p=0.012), respectively. Spearman’s correlation between per cent area myxovirus 1 protein immunoreactivity and IFN-dominant mRNA gene cluster expression was highly significant (dermis, rho=0.86, p<0.001). In total, skin tape-derived RNA expression comprising both IFN-dominant and CLE-associated gene clusters correlated with per cent area immunoreactivity of some hallmark CLE-associated proteins in punch biopsies from the same lesions.

Conclusions

A non-invasive tape RNA collection technique is a potential tool for repeated skin biomarker measures throughout a clinical trial.

Tape strips in dermatology research

Tape strips have been used widely in dermatology research as a minimally invasive method to sample the epidermis, avoiding the need for skin biopsies. Most research has focused on epidermal pathology, such as atopic eczema, but there is increasing research into the use of tape strips in other dermatoses, such as skin cancer, and the microbiome. This review summarizes the technique of tape stripping, and discusses which dermatoses have been studied by tape stripping and alternative minimally invasive sampling methods. We review the number of tape strips needed from each patient and the components of the epidermis that can be obtained by tape stripping. With a focus on protein and RNA extraction, we address the techniques used to process tape strips. There is no optimal protocol to extract protein, as this depends on the abundance of the protein studied, its level of expression in the epidermis and its solubility. Many variables can alter the amount of protein obtained from tape strips, which must be standardized to ensure consistency between samples. No study has compared different RNA extraction techniques, but our own experience is that RNA yield is optimized by using 20 tape strips and the use of a cell scraper.

Skin lipids in health and disease: A review

Our skin is the interface between us and our environment - a flexible barrier that has evolved for protection, immunity, regulation and sensation. Once regarded as inert, we now know that it is a dynamic environment. Skin lipids are crucial to the structure and function of skin. From deep in the hypodermis, through the ceramide-rich epidermis, to the lipids of the skin surface, there are a vast array of different lipids with important roles to play. This review firstly discusses the lipid composition of human skin and secondly, changes that have been found in skin lipid composition in different skin diseases. Further research into skin lipids facilitated by ever-improving methodologies will no doubt generate new knowledge, paving the way for diagnosis, prevention and treatment of skin disorders and diseases.

Proteomic analysis from skin swabs reveals a new set of proteins identifying skin impairment in atopic dermatitis

Atopic Dermatitis (AD) is a common inflammatory skin disease characterized by skin and systemic inflammation, and barrier dysfunction. Herein, we investigate the proteomic profile of AD skin barrier to identify a unique signature with an easy-performed sampling approach. We enrolled 8 moderate-to-severe AD patients and 8 age- and gender-matched healthy controls. Swabs were obtained from non-lesional skin of retroauricular area and antecubital fold. Peptide mixtures obtained through protein precipitation and in-solution digestion were analysed using NanoLC-MS/MS. Label-free quantification and statistical analysis were conducted in MaxQuant and Perseus. Bioinformatics analysis was performed using Gene Ontology and STRING. We identified 908 proteins and 35 differentially expressed proteins were selected (fold change 2, FDR < 0.05). Particularly, AD skin showed downregulation of skin hydration factors, structural and epidermal proteins, abnormalities in protease-proteasome complex and lipid metabolism profile. Imbalance of antioxidant and inflammatory processes, along with TDRD15 upregulation was also observed. Our result showed partial overlap with skin biopsy/tape-strips studies, showing the reliability of our sampling approach which could be an easier method of detection of hallmark barrier proteins in AD. Furthermore, we displayed a new differentially expressed set of proteins, not yet explored in AD which can have a potential role in AD pathomechanisms.

Tape strips from early-onset pediatric atopic dermatitis highlight disease abnormalities in nonlesional skin

BACKGROUND

Skin biopsies promote our understanding of atopic dermatitis/AD pathomechanisms in infants/toddlers with early-onset AD, but are not feasible in pediatric populations. Tape strips are an emerging, minimally invasive alternative, but global transcriptomic profiling in early pediatric AD is lacking. We aimed to provide global lesional and nonlesional skin profiles of infants/toddlers with recent-onset, moderate-to-severe AD using tape strips.

METHODS

Sixteen tape strips were collected for RNA-seq profiling from 19 infants/toddlers (<5 years old; lesional and nonlesional) with early-onset moderate-to-severe AD (≤6 months) and 17 healthy controls.

RESULTS

We identified 1829 differentially expressed genes/DEGs in lesional AD and 662 DEGs in nonlesional AD, vs healthy skin (fold-change ≥2, FDR <0.05), with 100% sample recovery. Both lesional and nonlesional skin showed significant dysregulations of Th2 (CCL17 and IL4R) and Th22/Th17 (IL36G, CCL20, and S100As)-related genes, largely lacking significant Th1-skewing. Significant down-regulation of terminal differentiation (FLG and FLG2), lipid synthesis/metabolism (ELOVL3 and FA2H), and tight junction (CLDN8) genes were primarily seen in lesional AD. Significant negative correlations were identified between Th2 measures and epidermal barrier gene-subsets and individual genes (FLG with IL-4R and CCL17; r < -0.4, P < .05). Significant correlations were also identified between clinical measures (body surface area/BSA, pruritus ADQ, and transepidermal water loss/TEWL) with immune and barrier mRNAs in lesional and/or nonlesional AD (FLG/FLG2 with TEWL; r < -0.4, P < .05).

CONCLUSION

RNA-seq profiling using tape strips in early-onset pediatric AD captures immune and barrier alterations in both lesional and nonlesional skin. Tape strips provide insight into disease pathomechanisms and cutaneous disease activity.

Vitiligo Skin Biomarkers Associated With Favorable Therapeutic Response

Vitiligo is an acquired depigmentation skin disease caused by immune-mediated death of melanocytes. The most common treatment for vitiligo is narrow band ultraviolet B phototherapy, which often is combined with topical therapies such as tacrolimus. However, patients' responses to these treatments show large variations. To date, the mechanism for this heterogeneity is unknown, and there are no molecular indicators that can predict an individual patient's response to therapy. The goal of this study is to identify clinical parameters and gene expression biomarkers associated with vitiligo response to therapy. Six patients with segmental vitiligo and 30 patients with non-segmental vitiligo underwent transcriptome sequencing of lesional and nonlesional skin at baseline before receiving combined UBUVB and tacrolimus therapy for 6 month, and were separated into good response and bad response groups based on target lesion achieving > 10% repigmentation or not. Our study revealed that treatment-responsive vitiligo lesions had significantly shorter disease duration compared with non-responsive vitiligo lesions (2.5 years vs 11.5 years, p=0.046, t-Test), while showing no significant differences in the age, gender, ethnicity, vitiligo subtype, or disease severity. Transcriptomic analyses identified a panel of 68 genes separating the good response from bad response lesions including upregulation of immune active genes, such as CXCL10, FCRL3, and TCR, Further, compared with vitiligo lesions with long disease duration, the lesions with short duration also have much higher level of expression of immune-active genes, including some (such as FCRL3 and TCR genes) that are associated with favorable therapeutic response. In conclusion, our study has identified clinical parameters such as short disease duration and a panel of immune active and other gene expression biomarkers that are associated with favorable response to immune suppressive NBUVB + tacrolimus therapy. These markers may be useful clinically for individualized therapeutic management of vitiligo patients in the future.

Skin tape sampling technique identifies proinflammatory cytokines in atopic dermatitis skin

BACKGROUND

Monitoring the effects of biologic therapies in skin diseases will benefit from alternative noninvasive skin sampling techniques to evaluate immune pathways in diseased tissue early and longitudinally.

OBJECTIVE

To establish a minimally invasive profiling of skin cytokines for diagnosis, therapeutic response monitoring, and clinical research in atopic dermatitis (AD) and other skin diseases, particularly in pediatric cohorts.

METHODS

We developed a novel method for cytokine profiling in the epidermis using skin tape strips (STSs) in a setting designed to maximize the efficiency of protein extraction from STSs. This method was applied to analyze STS protein extracts from the lesional skin of children having AD (n = 41) and normal, healthy controls (n = 22). A total of 20 cytokines were probed with the ultrasensitive Mesoscale multiplex cytokine assay.

RESULTS

A significant increase in interleukin (IL)-1b (P < .01), IL-18 (P < .001), and IL-8 (P < .001) with a decrease in IL-1a (P < .001) in the stratum corneum of AD lesional skin was found. Concurrently, an increase in markers associated with type 2 inflammatory response was readily detectable in AD lesional skin, including C-C motif chemokine ligand (CCL) 22, CCL 17, and thymic stromal lymphopoietin (TSLP). The levels of IL-1b, IL-18, and TSLP exhibited positive correlations with the AD severity index (Scoring AD index) and skin transepidermal water loss (TEWL), whereas an inverse correlation between IL-1a and Scoring AD index and IL-1a and TEWL was found. The levels of CCL17, CCL22, TSLP, IL-22, and IL-17a correlated with skin TEWL measurements.

CONCLUSION

Using minimally invasive STS analysis, we identified cytokine profiles easily sampled in AD lesional skin. The expression of these markers correlated with disease severity and reflected changes in TEWL in lesional skin. These markers suggest new response assessment targets for AD skin.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03168113.

Cytokine concentration across the stratum corneum in atopic dermatitis and healthy controls

Tape stripping is a promising technique for assessment of epidermal biomarkers in inflammatory skin diseases. However, to facilitate its implementation in the clinical practice, a thorough validation regarding sampling strategy is needed. Knowledge of biomarkers variation in concentration across stratum corneum is scarce. Therefore, this study aimed to assess the variability of cytokines across stratum corneum using tape stripping technique by consecutive application of 21 adhesive tapes (D-squame) to lesional and non-lesional skin from 15 patients with atopic dermatitis (AD) and 16 healthy controls. Concentration of cytokines (IL-1α, IL-1b, IL-5, IL-18, IFN-γ, CCL17, CCL22, CCL27, CXCL8, CXCL10, TNF-α, TSLP, VEGFA) was determined in five different depths, using multiplex immunoassay. Comparing tape 4 with tape 21, no cytokine changed significantly in concentration in AD lesional skin. In AD non-lesional skin a small decrease was found for CCL17, CXCL8 and CXCL10. For healthy controls, a decrease was found for IL-1a, IL-1b, VEGFA and an increase for IL-18. Differences were found between AD skin and healthy control skin. Concentration of cytokines was stable across stratum corneum, indicating that sampling of only one tape from the stratum corneum is reliable in reflecting the overall cytokine milieu. Differences between AD and healthy skin confirm robustness of tape stripping for measuring cytokine levels.

Topical corticosteroids normalize both skin and systemic inflammatory markers in infant atopic dermatitis

Background

Atopic dermatitis (AD) is the most common inflammatory skin disease. It is highly heterogeneous in clinical presentation, treatment response, disease trajectory and associated atopic comorbidities. Immune biomarkers are dysregulated in skin and peripheral blood.

Aims

We used noninvasive skin and peripheral biomarkers to observe the effects of real‐world topical corticosteroid (TCS) treatment in infants with AD, by measuring skin and blood biomarkers before and after therapy.

Methods

Seventy‐four treatment‐naïve infants with AD underwent 6 weeks of TCS treatment. Stratum corneum (SC) and plasma blood biomarkers as well as SC natural moisturizing factor (NMF) were measured before and after TCS therapy. Immune markers included innate, T helper (Th)1 and Th2 immunity, angiogenesis, and vascular factors. AD severity was assessed by the Scoring Atopic Dermatitis index, and skin barrier function by transepidermal water loss (TEWL). Twenty healthy infants were recruited as controls.

Results

TCS therapy predictably led to improvement in disease severity. Levels of immune markers in the skin and in the peripheral blood showed significant change from baseline, though most did not reach healthy control levels. The most prominent change from baseline in the SC was in markers of innate immune activation, interleukin (IL)‐18, IL‐8 and IL‐1α, and the Th2 chemokines C‐C motif chemokine (CCL)17 and CCL22. In blood, the largest changes were in Th2‐skewed biomarkers: CCL17, IL‐13, CCL22, IL‐5, and CCL26. TEWL decreased after therapy; no significant changes from baseline were found for NMF.

Conclusions

The profound impact of topical therapy on systemic biomarkers suggests that the skin compartment generates a major component of dysregulated systemic cytokines in infant AD. There may be long‐term beneficial effects of correcting systemic immune dysregulation through topical therapy.

What is already known about this topic?

Atopic dermatitis (AD) is a clinically heterogeneous condition with multiple clinical manifestations and a complex pathogenesis.

Noninvasive sampling of the stratum corneum has yielded significant insights into cytokine profiles of this compartment in AD.

Peripheral blood signatures have distinct cytokine profiles in childhood AD.

What does this study add?

We show the effects of topical corticosteroid (TCS) therapy on both skin‐derived and peripheral blood biomarkers.

TCS therapy had an effect on the cutaneous compartment but also substantially normalized the peripheral blood compartment cytokine signatures.

The long‐term effects of normalizing peripheral immune signatures are unknown but could potentially be beneficial.

What is the translational message?

TCS therapy can normalize systemic immune dysregulation in infant AD.

Tape-Strip Proteomic Profiling of Atopic Dermatitis on Dupilumab Identifies Minimally Invasive Biomarkers

Tape-stripping is a minimally invasive approach for skin sampling that captures the cutaneous immune/barrier abnormalities in atopic dermatitis (AD). However, tape-strips have not been used to evaluate molecular changes with therapeutic targeting. In this study, we sought to characterize the proteomic signature of tape-strips from AD patients, before and after dupilumab therapy. Twenty-six AD patients were treated with every-other-week dupilumab 300 mg for 16 weeks. Tape-strips from lesional and non-lesional skin were collected before and after treatment, and analyzed with the Olink proteomic assay. Using criteria of fold-change>1.5 and FDR < 0.05, 136 proteins significantly decreased after dupilumab treatment, corresponding to an overall mean improvement of 66.2% in the lesional vs. non-lesional AD proteome. Significant decreases after dupilumab were observed in immune markers related to general inflammation (MMP12), Th2 (CCL13/CCL17), Th17/Th22 (IL-12B, CXCL1, S100A12), and innate immunity (IL-6, IL-8, IL-17C), while the Th1 chemokines CXCL9/CXCL10 remained elevated. Proteins related to atherosclerosis/cardiovascular risk (e.g., SELE/E-selectin, IGFBP7, CHIT1/ chitotriosidase-1, AXL) also significantly decreased after treatment. Dupilumab therapy suppressed AD-related immune biomarkers and atherosclerosis/cardiovascular risk proteins. Tape-strip proteomics may be useful for monitoring therapeutic response in real-life settings, clinical trials, and longitudinal studies for AD and beyond.

Stratum Corneum Biomarkers in Atopic Dermatitis: Biological and Spatial Variability

Background:

Atopic dermatitis is a highly heterogeneous skin disease, mainly affecting children. Introduction of biological therapies has urged the development of biomarkers to facilitate personalized therapy. Stratum corneum biomarkers emerged as a promising non-invasive alternative to skin biopsy, yet validation of spatial and biological variability is essential for their application in clinical research.

Objective:

To assess spatial and biological variability of stratum corneum biomarkers for atopic dermatitis.

Methods:

Stratum corneum was collected from 17 atopic dermatitis patients by consecutive application of eight adhesive tapes to a lesional skin site and 2 cm and 4 cm from the lesion. Two non-lesional sites at a 2 cm distance from the same lesion were collected to determine biological variability. Filaggrin degradation products (NMF) were determined by liquid chromatography and thirteen cytokines (IL-4, IL-13, IL-18, IL-31, IL-33, CCL17, CCL22, CCL27, CXCL8, IL-1α, IL-RA, IL-18, IL-22) by multiplex immunoassay.

Results:

Biomarker levels showed gradual changes from lesional to non-lesional skin sites at 2 cm and 4 cm; magnitude and direction of change were biomarker-specific. Intra-subject variability ranged from 17.3% (NMF) to 85.1% (CXCL8). Biomarker levels from two stratum corneum depths were highly correlated; several biomarkers showed significant depth dependence.

Conclusion:

Stratum corneum enables non-invasive collection of relevant immune and epidermal biomarkers, but biomarker-specific spatial and biological variability emphasizes the importance of standardized procedures for stratum corneum collection.

Review-Current Concepts in Inflammatory Skin Diseases Evolved by Transcriptome Analysis: In-Depth Analysis of Atopic Dermatitis and Psoriasis

During the last decades, high-throughput assessment of gene expression in patient tissues using microarray technology or RNA-Seq took center stage in clinical research. Insights into the diversity and frequency of transcripts in healthy and diseased conditions provide valuable information on the cellular status in the respective tissues. Growing with the technique, the bioinformatic analysis toolkit reveals biologically relevant pathways which assist in understanding basic pathophysiological mechanisms. Conventional classification systems of inflammatory skin diseases rely on descriptive assessments by pathologists. In contrast to this, molecular profiling may uncover previously unknown disease classifying features. Thereby, treatments and prognostics of patients may be improved. Furthermore, disease models in basic research in comparison to the human disease can be directly validated. The aim of this article is not only to provide the reader with information on the opportunities of these techniques, but to outline potential pitfalls and technical limitations as well. Major published findings are briefly discussed to provide a broad overview on the current findings in transcriptomics in inflammatory skin diseases.