Skin biomarkers predict development of atopic dermatitis in infancy

Early skin inflammatory biomarker is predictive of development and persistence of atopic dermatitis in infants

BACKGROUND

The Short-Term Topical Application for Prevention of Atopic Dermatitis (STOP AD) study, a randomized, open-label trial evaluating the effect of short-term (from the first 4 postnatal days to age 8 weeks) skin barrier protection using Aveeno Dermexa Fast & Long-Lasting Balm (Johnson & Johnson, New Brunswick, NJ) in infants with a parent with allergic disease, demonstrated decreased cumulative incidence and decreased prevalence of atopic dermatitis (AD) at age 12 months.

OBJECTIVE

In the STOP AD study, we aimed to identify skin biomarkers that are associated with risk of development of AD.

METHODS

Skin swabs were collected from the cheek and antecubital fossa (AF) at baseline, age 8 weeks, and age 12 months from subsets of study participants from the intervention arm (n = 43 of 119) and control arm (n = 43 of 138) and were analyzed for specific cytokines (CCL27, CXCL2, human β-defensin-1 [hBD-1], IL-18, IL-8, IL-1α, IL-1 receptor antagonist [IL-1RA], IL-1β, S100A8/9, and IL-36γ) by ELISA.

RESULTS

Higher titers of S100A8/9 at the AF at age 8 weeks in infants with the filaggrin wild-type genotype (FLGwt), but not in those with filaggrin loss-of-function mutation (FLGmut), predicted (1) development of AD in the first year of life (P = .033), (2) presence of AD at ages 6 or 12 months (P = .009 and .035, respectively), (3) persistence of AD between ages 6 and 12 months (P < .001), and (4) development of AD with the emollient intervention.

CONCLUSION

Increased titers of S100A8/9 from skin swabs of the AF in high-risk infants at age 8 weeks with FLGwt were predictive of AD development in the first year of life and other AD features. These findings suggest that there are different molecular pathways leading to AD in individuals with FLGmut and in individuals with FLGwt. Early identification of infants who are likely to develop AD will allow more targeted interventions.

Proteomic alterations in patients with atopic dermatitis

INTRODUCTION

Atopic Dermatitis (AD) is the most common inflammatory skin disease with a complex and multifactorial pathogenesis. The use of proteomics in understanding AD has yielded the discovery of novel biomarkers and may further expand therapeutic options.

AREAS COVERED

This review summarizes the most recent proteomic studies and the methodologies used in AD. It describes novel biomarkers that may monitor disease course and therapeutic response. The review also highlights skin and blood biomarkers characterizing different AD phenotypes and differentiates AD from other inflammatory skin disorders. A literature search was conducted by querying Scopus, Google Scholar, Pubmed/Medline, and Clinicaltrials.gov up to June 2023.

EXPERT OPINION

The integration of proteomics into research efforts in atopic dermatitis has broadened our understanding of the molecular profile of AD through the discovery of new biomarkers. In addition, proteomics may contribute to the development of targeted treatments ultimately improving personalized medicine. An increasing number of studies are utilizing proteomics to explore this heterogeneous disease.

Preclinical Atopic Dermatitis Skin in Infants: An Emerging Research Area

Whereas clinically apparent atopic dermatitis (AD) can be confirmed by validated diagnostic criteria, the preclinical phenotype of infants who eventually develop AD is less well-characterized. Analogous to unaffected or nonlesional skin in established AD, clinically normal-appearing skin in infants who will develop clinical AD has distinct changes. Prospective studies have revealed insights into this preclinical AD phenotype. In this study, we review the structural, immunologic, and microbiome nature of the preclinical AD phenotype. Determination of markers that predict the development of AD will facilitate targeting of interventions to prevent the development or reduce the severity of AD in infants.

Spatial modeling connecting childhood atopic dermatitis prevalence with household exposure to pollutants

BACKGROUND

Atopic dermatitis (AD) is a chronic, inflammatory disease characterized by dry, pruritic skin. In the U.S., the prevalence of AD has increased over three-fold since the 1970s. We previously reported a geographic association between isocyanate-containing air pollution and AD as well as mechanistic data demonstrating that isocyanates induce skin dysbiosis and activate the host itch receptor TRPA1. However, non-spatial models are susceptible to spatial confounding and may overlook other meaningful associations.

METHODS

We added spatial analysis to our prior model, contrasting pollution data with clinical visits. In addition, we conducted a retrospective case-control survey of childhood exposure to BTEX-related products. Finally, we assessed implicated compounds, in pure form and as part of synthetic fabric, for their effect on the growth and metabolism of skin commensal bacteria.

RESULTS

Spatial analysis implicate benzene, toluene, ethylbenzene, and, most significantly, xylene (BTEX) compounds. Survey odds ratios for AD were significant for xylene-derived polyester bed sheets (OR = 9.5; CI 2.2-40.1) and diisocyanate-containing wallpaper adhesive (OR = 6.5; CI 1.5-27.8). Staphylococcus aureus lives longer on synthetic textiles compared to natural textiles. Meanwhile, synthetic fabric exposure shifts the lipid metabolism of health-associated commensals (Roseomonas mucosa and S. epidermidis) away from therapeutic pathways.

CONCLUSIONS

We propose that BTEX chemicals in their raw forms and in synthetic products represent a unifying hypothesis for environmentally induced AD flares through their ability to create dysbiosis in the skin microbiota and directly activate TRPA1. Unequal distribution of these pollutants may also influence racial disparities in AD rates.

The circadian metabolome of atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by dry, pruritic skin. Several studies have described nocturnal increases in itching behavior, suggesting a role for the circadian rhythm in modulating symptom severity. However, the circadian rhythm of metabolites in the skin and serum of patients with AD is yet to be described.

OBJECTIVE

We sought to assess circadian patterns of skin and serum metabolism in patients with AD.

METHODS

Twelve patients with moderate to severe AD and 5 healthy volunteers were monitored for 28 hours in a controlled environment. Serum was collected every 2 hours and tape strips every 4 hours from both lesional and nonlesional skin in participants with AD and location-, sex-, and age-matched healthy skin of controls. We then performed an untargeted metabolomics analysis, examining the circadian peaks of metabolism in patients with AD.

RESULTS

Distinct metabolic profiles were observed in AD versus control samples. When accounting for time of collection, the greatest differences in serum metabolic pathways were observed in arachidonic acid, steroid biosynthesis, and terpenoid backbone biosynthesis. We identified 42 circadian peaks in AD or control serum and 17 in the skin. Pathway enrichment and serum-skin metabolite correlation varied throughout the day. Differences were most evident in the late morning and immediately after sleep onset.

CONCLUSIONS

Although limited by a small sample size and observational design, our findings suggest that accounting for sample collection time could improve biomarker detection studies in AD and highlight that metabolic changes may be associated with nocturnal differences in symptom severity.

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.

Association between skin barrier development and early-onset atopic dermatitis: A longitudinal birth cohort study

BACKGROUND

A diagnosis of atopic dermatitis (AD) is common during infancy; however, it is unclear whether differential skin barrier development defines this period and signals disease onset in predisposed individuals.

OBJECTIVE

We sought to study (NCT03143504) and assess the feasibility of remote skin testing from birth to monitor skin barrier maturation and model association with an AD diagnosis by age 12 months.

METHODS

Biophysical testing and infrared spectroscopy were conducted at the maternity ward and family home. Tape stripping collected samples for desquamatory protease and natural moisturizing factor analysis. The 4 common European filaggrin risk alleles were screened.

RESULTS

A total of 128 infants completed the study, with 20% developing mild disease. Significant changes in permeability barrier function, desquamatory protease activity, and molecular composition assessed spectroscopically were observed longitudinally, but only subtle evidence of differential skin barrier development was noted between infant subgroups. Common filaggrin risk alleles were strongly associated with early-onset disease and conferred a significant reduction in natural moisturizing factor and water content by age 4 weeks. Accounting for a family history of atopy, these parameters alongside a greater lipid/protein ratio and reduced chymotrypsin-like activity at birth were associated with AD. Measured in ambient conditions, transepidermal water loss did not signal disease risk at any stage.

CONCLUSIONS

Skin barrier dysfunction lacked an acquired modality but was considered proportional to cohort severity and suggests that a portfolio of tests used in a community setting has the potential to improve current AD risk evaluations from birth.

Stratum corneum and microbial biomarkers precede and characterize childhood atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is the most common paediatric inflammatory skin disease. There are currently no robust biomarkers that could reliably predict its manifestation, and on the molecular level, it is less well characterized than adult AD.

OBJECTIVES

This study aimed to extend previous findings and provide evidence for distinct changes of the epidermal proteome and microbiome preceding the onset of AD as well as characterizing early AD.

METHODS

We longitudinally analysed epidermal biomarker levels and microbial profiles in a cohort of 50 neonates at high risk for AD, who had participated in a randomized controlled trial on early emollient use for AD prevention.

RESULTS

About 26% of the infants developed AD until month 24 with an average age of 10 month at disease onset. In children with later AD, IL-1Ra, TNFβ, IL-8, IL-18, IL-22, CCL2, TARC, TSLP and VEGFa showed increased levels prior to disease manifestation with levels of IL-1Ra, TNFβ and VEGFa already increased shortly after birth. Further, children with later AD displayed a delayed maturation and differentially composed skin microbiome prior to AD onset. At manifestation, levels of multiple Th2, Th17/22 and Th1-associated biomarkers as well as innate immunity markers were elevated, and abundances of commensal Streptococcus species were reduced in favour of Staphylococcus epidermidis.

CONCLUSIONS

Our results indicate that elevations of proinflammatory stratum corneum biomarkers and alterations of the skin microbiome precede paediatric AD and characterize the disease at onset.

Ethnic endotypes in paediatric atopic dermatitis depend on immunotype, lipid composition and microbiota of the skin

BACKGROUND

Atopic dermatitis (AD) endotypes differ with ethnicity. We examined the skin microbiota, cytokine and lipid profiles in Greenlandic Inuit and Danish children with AD.

METHODS

Twenty-five Inuit children with AD and 25 Inuit control children were clinically examined and compared to previously collected data from 25 Danish children with AD. Skin tape strips and skin swabs were collected from lesional and non-lesional skin. Levels of cutaneous immune biomarkers, free sphingoid bases and their (glycosyl)ceramides were analysed. Skin swabs were analysed with 16S rRNA and tuf gene for characterization of bacterial species communities.

RESULTS

Bacterial β-diversity was significantly different between Inuit and Danish AD skin, in both lesional (p < 0.001) and non-lesional (p < 0.001) AD skin, and there was a higher relative abundance of Staphylococcus aureus in Danish compared to Inuit lesional (53% vs. 8%, p < 0.01) and non-lesional skin (55% vs. 5%, p < 0.001). Danish AD children had a higher α-diversity than Inuit children in non-lesional (p < 0.05) but not in lesional skin. Significantly higher levels of type 2 immunity cytokine interleukin (IL)-4 (p < 0.05) and IL-5 (p < 0.01) were identified in Inuit compared to Danish AD children. In contrast, IL-33 (p < 0.01) was higher in Danish lesional and non-lesional AD skin. Higher levels of long-chain glucosylceramide (GlcCER)[S](d26:1) were found in lesional (p < 0.001) and non-lesional (p < 0.001) Inuit skin compared with Danish AD skin. NMF levels were similar in Inuit and Danish AD skin.

CONCLUSION

Skin microbiota, cytokine and lipid composition differed significantly between Inuit and Danish children with AD and showed a stronger type 2 immune signature in Inuit children.

A Retrospective Analysis of Risk Factors for Atopic Dermatitis Severity

Background: Atopic dermatitis (AD) has the highest burden of any skin disease; however, the severity-associated factors remain unclear. Objective: To evaluate potential severity-associated factors of AD and to design and validate a severity prediction model to inform the management of AD patients. Methods: A cross-sectional study of 900 AD patients was conducted from December 2021 to October 2022 at our hospital. The primary outcome was disease severity, categorized as mild, moderate, or severe using the scoring atopic dermatitis index. Ordinal logistic regression and bootstrapped validation were used to derive and internally validate the model. Results: Increasing age, elevated eosinophil level, higher economic status, and urban residence were associated with severe AD. Breastfeeding, disinfectants and topical emollients use, and short duration of bathing were associated with mild AD. In the prediction model, predictors included age, eosinophil and economic status, residence, feeding, disinfectants and emollients use, and duration of bathing. Prediction models demonstrated good discrimination (bias-corrected concordance index [c-index] = 0.72) and good calibration. Conclusion: Risk factors for the severity of AD were identified that could aid the early prediction of AD progression. The predictive model included variables that are easily evaluated and could inform personalized prevention and therapy.

Electrical impedance spectroscopy detects skin barrier dysfunction in childhood atopic dermatitis

BACKGROUND

Skin barrier dysfunction is associated with the development of atopic dermatitis (AD), however methods to assess skin barrier function are limited. We investigated the use of electrical impedance spectroscopy (EIS) to detect skin barrier dysfunction in children with AD of the CARE (Childhood AlleRgy, nutrition, and Environment) cohort.

METHODS

EIS measurements taken at multiple time points from 4 months to 3-year-old children, who developed AD (n = 66) and those who did not (n = 49) were investigated. Using only the EIS measurement and the AD status, we developed a machine learning algorithm that produces a score (EIS/AD score) which reflects the probability that a given measurement is from a child with active AD. We investigated the diagnostic ability of this score and its association with clinical characteristics and age.

RESULTS

Based on the EIS/AD score, the EIS algorithm was able to clearly discriminate between healthy skin and clinically unaffected skin of children with active AD (area under the curve 0.92, 95% CI 0.85-0.99). It was also able to detect a difference between healthy skin and AD skin when the child did not have active AD. There was no clear association between the EIS/AD score and the severity of AD or sensitisation to the tested allergens. The performance of the algorithm was not affected by age.

CONCLUSIONS

This study shows that EIS can detect skin barrier dysfunction and differentiate skin of children with AD from healthy skin and suggests that EIS may have the ability to predict future AD development.

CLA+ memory T cells in atopic dermatitis: CLA+ T cells and atopic dermatitis

Circulating skin-homing cutaneous lymphocyte-associated antigen (CLA)+ T cells constitute a small subset of human memory T cells involved in several aspects of atopic dermatitis: Staphylococcus aureus related mechanisms, the abnormal Th2 immune response, biomarkers, clinical aspects of the patients, pruritus, and the mechanism of action of targeted therapies. Superantigens, IL-13, IL-31, pruritus, CCL17 and early effects on dupilumab-treated patients have in common that they are associated with the CLA+ T cell mechanisms in atopic dermatitis patients. The function of CLA+ T cells corresponds with the role of T cells belonging to the skin-associated lymphoid tissue and could be a reason why they reflect different mechanisms of atopic dermatitis and many other T cell mediated skin diseases. The goal of this review is to gather all this translational information of atopic dermatitis pathology.

Cytokines and Epidermal Lipid Abnormalities in Atopic Dermatitis: A Systematic Review

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease and presents a major public health problem worldwide. It is characterized by a recurrent and/or chronic course of inflammatory skin lesions with intense pruritus. Its pathophysiologic features include barrier dysfunction, aberrant immune cell infiltration, and alterations in the microbiome that are associated with genetic and environmental factors. There is a complex crosstalk between these components, which is primarily mediated by cytokines. Epidermal barrier dysfunction is the hallmark of AD and is caused by the disruption of proteins and lipids responsible for establishing the skin barrier. To better define the role of cytokines in stratum corneum lipid abnormalities related to AD, we conducted a systematic review of biomedical literature in PubMed from its inception to 5 September 2023. Consistent with the dominant TH2 skewness seen in AD, type 2 cytokines were featured prominently as possessing a central role in epidermal lipid alterations in AD skin. The cytokines associated with TH1 and TH17 were also identified to affect barrier lipids. Considering the broad cytokine dysregulation observed in AD pathophysiology, understanding the role of each of these in lipid abnormalities and barrier dysfunction will help in developing therapeutics to best achieve barrier homeostasis in AD patients.

The association between Staphylococcus aureus colonization on cheek skin at 2 months and subsequent atopic dermatitis in a prospective birth cohort

BACKGROUND

Staphylococcus aureus may worsen already established atopic dermatitis (AD), but its primary role in the aetiopathogenesis and severity of AD is unclear.

OBJECTIVES

To compare the prevalence of S. aureus colonization in early infancy in children who developed AD during the first 2 years of life with children who did not.

METHODS

In this prospective birth cohort study, which included 450 infants, we analysed bacterial swabs collected from cheek skin at 0 and 2 months of age. The development of AD, and its severity, was diagnosed by a physician and monitored prospectively for 2 years. Information on parental atopy, filaggrin gene mutation status and use of antibiotics and emollients was included in the analyses.

RESULTS

At birth, the occurrence of S. aureus colonization was similar in infants who developed subsequent AD and those who did not. At 2 months of age, S. aureus colonization was more common in children who later developed AD (adjusted hazard ratio 1.97, 95% confidence interval 1.21-3.19; P = 0.006). No association was found between S. aureus colonization and AD severity or age at onset.

CONCLUSIONS

It remains unknown whether colonization with S. aureus may directly increase the risk of AD, or whether it should be considered as secondary to skin barrier impairment or a skewed immune activity, but according to our findings, S. aureus colonization is more commonly increased at 2 months of age in children who later developed AD.

Trajectory of stratum corneum lipid subclasses in the first year of life and associations with atopic dermatitis: A prospective cohort study

BACKGROUND

Trajectories of stratum corneum (SC) lipid subclasses and their associations with infant atopic dermatitis (AD) are unclear. This study aimed to quantify the trajectories of 15 SC subclasses and carbon chain lengths and their associations with AD within 12 months.

METHODS

In total, 213 newborns were enrolled at birth with nonlesional skin samples collected from the inner forearm at birth, 42 days, 3, 6, and 12 months, respectively. Lesional skin samples were collected from 120 AD patients at clinic with the disease onset within the first year of life. Mass spectrometry was applied to assess relative contents of 12 ceramide (CER), three free fatty acid (FFA) subclasses, and average carbon chain length (CCL). AD incident within 1 year old was diagnosed by dermatologists according to UK criteria.

RESULTS

Sixty-four (30.0%) cases of ADs occurred in the cohort. All SC lipid subclasses and CCLs, but EOP varied significantly during the first year. AD infants showed lower NP but higher NS, NH, AP, hydroxy FFA, and CCL of FFAs compared with nonaffected infants. After normalization by age, the differences remained and were more pronounced in lesional skin of clinical AD infants compared with non-ADs. NS, NH, and CCL of FFAs in lesional skin of AD infants showed positive and significant correlations with the levels of transepidermal water loss at 3 month; some evidence supports a negative correlation for NP.

CONCLUSIONS

We provide an overview of developmental trajectories of 15 CER and FFA subclasses across the first year of healthy infants and a link between the imbalance of some subclasses with the development of AD.

Epidermal biomarkers of the skin barrier in atopic and contact dermatitis

Dysfunction of the skin barrier plays a critical role in the initiation and progression of inflammatory skin diseases, such as atopic dermatitis and contact dermatitis. Epidermal biomarkers can aid in evaluating the functionality of the skin barrier and understanding the mechanisms that underlay its impairment. This narrative review provides an overview of recent studies on epidermal biomarkers associated with the function and integrity of the skin barrier, and their application in research on atopic dermatitis and contact dermatitis. The reviewed studies encompass a wide spectrum of molecular, morphological and biophysical biomarkers, mainly obtained from stratum corneum tape strips and biopsies. Lipids, natural moisturizing factors, and structural proteins are the most frequently reported molecular biomarkers. Additionally, corneocyte surface topography and elasticity show potential as biomarkers for assessing the physical barrier of the skin. In contact dermatitis studies, biomarkers are commonly employed to evaluate skin irritation and differentiate between irritant and allergic contact dermatitis. In atopic dermatitis, biomarkers are primarily utilized to identify differences between atopic and healthy skin, for predictive purposes, and monitoring response to therapies. While this overview identifies potential biomarkers for the skin barrier, their validation as epidermal biomarkers for atopic dermatitis and contact dermatitis has yet to be established.

Reduced Skin Microbiome Diversity in Infancy Is Associated with Increased Risk of Atopic Dermatitis in High-Risk Children

It is currently unknown whether alterations in the skin microbiome exist before development of atopic dermatitis (AD). In this prospective Danish birth cohort of 300 children, we examined whether skin microbiome alterations during the first 2 months of life were associated with an increased risk of AD in the first 2 years and its severity after adjustment for environmental factors and selected skin chemokine and natural moisturizing factor levels. We found no overall association between the skin microbiome at birth and age 2 months and AD during the first 2 years of life. However, when restricting the analysis to children with at least one parent with atopy, a lower alpha diversity at age 2 months was associated with an increased risk of AD (adjusted hazard ratio = 1.7, 95% confidence interval = 1.1-2.6). We observed a stronger association in children where both parents had atopy (adjusted hazard ratio = 4.4, 95% confidence interval = 1.1-18.2). The putative pathogenic role of changes in the skin microbiome on AD risk remains uncertain but may play a role in those with an atopic predisposition.

The minichromosome maintenance complex drives esophageal basal zone hyperplasia

Eosinophilic esophagitis (EoE) is a chronic gastrointestinal disorder characterized by food antigen-driven eosinophilic inflammation and hyperproliferation of esophageal mucosa. By utilizing a large-scale, proteomic screen of esophageal biopsies, we aimed to uncover molecular drivers of the disease. Proteomic analysis by liquid chromatography-tandem mass spectrometry identified 402 differentially expressed proteins (DEPs) that correlated with the EoE transcriptome. Immune cell-related proteins were among the most highly upregulated DEPs in EoE compared with controls, whereas proteins linked to epithelial differentiation were primarily downregulated. Notably, in the inflamed esophageal tissue, all 6 subunits of the minichromosome maintenance (MCM) complex, a DNA helicase essential for genomic DNA replication, were significantly upregulated at the gene and protein levels. Furthermore, treating esophageal epithelial cells with a known inhibitor of the MCM complex (ciprofloxacin) blocked esophageal epithelial proliferation. In a murine model of EoE driven by overexpression of IL-13, ciprofloxacin treatment decreased basal zone thickness and reduced dilated intercellular spaces by blocking the transition of epithelial cells through the S-phase of the cell cycle. Collectively, a broad-spectrum proteomic screen has identified the involvement of the MCM complex in EoE and has highlighted MCM inhibitors as potential therapeutic agents for the disease.

Disease modification in inflammatory skin disorders: opportunities and challenges

Progress in understanding of the mechanisms underlying chronic inflammatory skin disorders, such as atopic dermatitis and psoriasis vulgaris, has led to new treatment options with the primary goal of alleviating symptoms. In addition, this knowledge has the potential to inform on new strategies aimed at inducing deep and therapy-free remission, that is, disease modification, potentially impacting on associated comorbidities. However, to reach this goal, key areas require further exploration, including the definitions of disease modification and disease activity index, further understanding of disease mechanisms and systemic spillover effects, potential windows of opportunity, biomarkers for patient stratification and successful intervention, as well as appropriate study design. This Perspective article assesses the opportunities and challenges in the discovery and development of disease-modifying therapies for chronic inflammatory skin disorders.

Lipid Differences and Related Metabolism Present on the Hand Skin Surface of Different-Aged Asiatic Females-An Untargeted Metabolomics Study

This cross-sectional study aimed to investigate differences in skin surface lipids (SSL) and explore related metabolic pathways among females of different ages in Henan Province. Ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) was used to determine the lipid composition of the skin surface of 58 female volunteers who were divided into three age groups. Statistical analysis was performed using Progenesis QI, Ezinfo, and MetaboAnalyst. Multivariate and enrichment analysis were used to identify the different SSL among the groups. A total of 530 lipid entities were identified and classified into eight classes. Among these, 63 lipids were significantly different between the groups. Lower levels of glycerolipids (GLs) and sphingolipids (SPs) were observed in the middle-aged group, while higher levels of GLs were found in the elder group. GLs belonged to the largest and statistically significant enrichment of lipid metabolic pathways, and the lipid individuals enriched to the sphingoid bases metabolism were the most and statistically significant. These findings suggest that there are differences in hand SSL among females of different ages, which may be related to GLs and sphingoid bases metabolism.

Current insights into skin lipids and their roles in cutaneous health and disease

PURPOSE OF REVIEW

The unique and complex array of cutaneous lipids include essential components of the skin structure and signalling molecules mediating homeostasis and inflammation. Understanding skin lipid biology and metabolism can support our comprehension of health and disease, including systemic conditions with cutaneous involvement.

RECENT FINDINGS

Lipids found on the skin surface, produced by both the host and resident microbes, maintain and regulate the skin microbiome and the epidermal barrier, whilst altered contributions from either source can be detrimental to skin health. The unique lipid composition of the epidermal barrier is essential for its function, and recent studies have expanded our understanding of epidermal ceramide production. This has been supported by improved models available for skin research, including organotypic skin models enabling in-vitro production of complex acylceramides for the first time, and model systems facilitating in-silico exploration of the lipid profile changes observed in clinical samples. Studies have revealed further involvement of lipid mediators such as eicosanoids in cutaneous inflammation, as well as immune regulation in both healthy and diseased skin.

SUMMARY

Skin lipids offer exciting opportunities as therapeutic targets for many conditions, whether through topical interventions or nutritional supplementation.

Stratum corneum lipid and cytokine biomarkers at age 2 months predict the future onset of atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) commonly occurs in children and can progress into severe phenotypes or atopic march, causing significant impairment in quality of life. It is important to find early biomarkers of future onset of AD before any clinical manifestations.

OBJECTIVE

We sought to find early predictors of future onset of AD in skin stratum corneum (SC).

METHODS

Skin tape strips were collected from the forearm of newborns (n = 111) with and without family history of atopic diseases at the age of 2 months before any signs of clinical AD. Children were clinically monitored until they reached age 2 years to ensure the presence or absence of AD. Skin tape strips were subjected to lipidomic analyses by the liquid chromatography electrospray ionization tandem mass spectrometry and cytokine determination by Meso Scale Discovery U-Plex assay.

RESULTS

Overall, 22 of 74 (29.7%) and 5 of 37 (13.5%) infants developed AD in the risk group and the control group, respectively. In the SC of future AD children, protein-bound ceramides were decreased (P < .001), whereas unsaturated sphingomyelin species (P < .0001) and "short-chain" nonhydroxy fatty acid sphingosine and alpha-hydroxy fatty acid sphingosine ceramides were elevated (P < .01 and .05, respectively) as compared with healthy children. Thymic stromal lymphopoietin and IL-13 levels were increased in the SC of future AD subjects (by 74.5% and 78.3%, P = .0022 and P < .0001, respectively). Multivariable logistic regression analysis revealed strong AD predicting power of the combination of family history, type 2 cytokines, and dysregulated lipids, with an odds ratio reaching 54.0 (95% CI, 9.2-317.5).

CONCLUSIONS

Noninvasive skin tape strip analysis at age 2 months can identify asymptomatic children at risk of future AD development with a high probability.

Biomarkers in atopic dermatitis

Atopic dermatitis (AD) is a complex and highly heterogeneous inflammatory skin disease. Given the highly heterogeneous character of AD, it is unlikely that every patient will respond equally to a particular treatment. The recent introduction of novel targeted therapies for AD has driven the need for patient stratification based on immunologic biomarkers. We have reviewed the use of different types of biomarkers as potential tools in the movement toward personalized medicine in AD, comprising different ways of endotyping patients with AD based on immunologic profiles and predictive biomarkers. The application of biomarkers will result in better characterization and stratification of patients and allow better comparison of current and new treatments. The ultimate goal will be to switch from the current generalized "one-drug-fits-all" management to more personalized "patient endotype-specific" management.

Skin TARC/CCL17 increase precedes the development of childhood atopic dermatitis

BACKGROUND

It is unknown whether skin biomarkers collected in infancy can predict the onset of atopic dermatitis (AD) and be used in future prevention trials to identify children at risk.

OBJECTIVES

This study sought to examine whether skin biomarkers can predict AD during the first 2 years of life.

METHODS

This study enrolled 300 term and 150 preterm children at birth and followed for AD until the age of 2 years. Skin tape strips were collected at 0 to 3 days and 2 months of age and analyzed for selected immune and barrier biomarkers. Hazard ratio (HR) with 95% confidence interval (CI) using Cox regression was calculated for the risk of AD.

RESULTS

The 2-year prevalence of AD was 34.6% (99 of 286) and 21.2% (25 of 118) among term and preterm children, respectively. Skin biomarkers collected at birth did not predict AD. Elevated thymus- and activation-regulated chemokine/C-C motif chemokine ligand 17 -levels collected at 2 months of age increased the overall risk of AD (HR: 2.11; 95% CI: 1.36-3.26; P = .0008) and moderate-to-severe AD (HR: 4.97; 95% CI: 2.09-11.80; P = .0003). IL-8 and IL-18 predicted moderate-to-severe AD. Low filaggrin degradation product levels increased the risk of AD (HR: 2.04; 95% CI: 1.32-3.15; P = .001). Elevated biomarker levels at 2 months predicted AD at other skin sites and many months after collection.

CONCLUSIONS

This study showed that noninvasively collected skin biomarkers of barrier and immune pathways can precede the onset of AD.

Potential biomarkers of atopic dermatitis

Atopic dermatitis (AD) is a chronic, recurrent inflammatory skin disease with a wide range of heterogeneity. Accurate biomarkers or predictors are the keys to instructing personalized tailored precise treatment. The development of technology such as transcriptomics, genomics, and proteomics provides novel insights into the possibility to find potential biomarkers. Meanwhile, emerging minimally invasive methods such as tape stripping were used to reveal different profiles of patients' skin without biopsy. Several potential biomarkers or predictors have been found. In this review, we summarized the current development of potential biomarkers of AD. Nitric oxide synthase 2/inducible nitric oxide synthase (NOS2/iNOS), human beta-defensin-2 (hBD-2), and matrix metalloproteinases 8/9 (MMP8/9) may be the candidate biomarkers for AD diagnosis. Filaggrin (FLG) gene mutation increased the occurrence risk of AD. Fatty-acid-binding protein 5 (FABP5) may serve as an effective biomarker for the atopic march (AM). Squamous cell carcinoma antigen 2 (SCCA2), serum thymus and activation-regulated chemokine (TARC), cutaneous T-cell-attracting chemokine (CTACK), eosinophil-derived neurotoxin (EDN), macrophage-derived chemokine (MDC), lactate dehydrogenase (LDH), and interleukin (IL)-18 can be the candidate biomarkers for disease severity monitoring. IL-17, IL-23, IL-33, and indoleamine 2,3-dioxygenase (IDO1) can be used as predictive biomarkers for AD comorbidities. LDH, TARC, pulmonary and activation-regulated chemokine (PARC), periostin, IL-22, eotaxin-1/3, and IL-8 may be the candidate biomarkers for monitoring treatment effects. There are still unmet needs and a long way to go for more convenient, non-invasive, and effective predictors and biomarkers to better guide personalized precise treatment.