Atopic dermatitis complicated by recurrent eczema herpeticum is characterized by multiple, concurrent epidermal inflammatory endotypes.

BACKGROUND: A subgroup of atopic dermatitis (AD) patients suffer from recurrent, disseminated herpes simplex virus (HSV) skin infections, termed eczema herpeticum (EH), which can be life-threatening and contribute to AD morbidity. The pathobiology underlying ADEH is unknown. OBJECTIVE: To determine transcriptional mechanisms of skin and immune system pathobiology that underlie ADEH disease. METHODS: We performed whole transcriptome RNA-sequencing of non-lesional skin samples (epidermis, dermis) of AD patients with (ADEH + , n=15) and without (ADEH - , n=13) recurrent EH history, and healthy controls (HC, n=15). We also performed RNA-sequencing on plasmacytoid dendritic cells (pDCs) collected from these participants and infected in vitro with HSV-1. Differential expression, gene set enrichment, and endotyping analyses were performed. RESULTS: ADEH + disease was characterized by dysregulation in skin gene expression, which was limited in dermis (differentially expressed genes [DEGs]=14) and widespread in epidermis (DEGs=129). ADEH + -upregulated epidermal DEGs were enriched in type 2 cytokine (T2) ( IL4R, CCL22, CRLF2, IL7R ), interferon ( CXCL10, ICAM1, IFI44 , and IRF7) , and IL-36γ ( IL36G ) inflammatory pathway genes. At a person-level, all ADEH + participants exhibited T2 and interferon endotypes and 87% were IL36G-high. In contrast, these endotypes were more variably expressed among ADEH - participants. ADEH + patient skin also exhibited dysregulation in epidermal differentiation complex (EDC) genes within the LCE, S100 , and SPRR families, which are involved in skin barrier function, inflammation, and antimicrobial activities. pDC transcriptional responses to HSV-1 infection were not altered by ADEH status. CONCLUSIONS: ADEH + pathobiology is characterized by a unique, multi-faceted epidermal inflammation that accompanies dysregulation in the expression of EDC genes. Key Messages: AD patients with a history of recurrent EH exhibit molecular skin pathobiology that is similar in form, but more severe in degree, than in AD patients without this complication. Non-lesional skin of ADEH + patients concurrently exhibits excessive type 2 cytokine, interferon, and IL-36γ-driven epidermal inflammation. Expression of these inflammatory skin endotypes among ADEH + patients is associated with dysregulation in expression of epidermal differentiation complex genes involved in barrier function, inflammation, and antimicrobial activity. Capsule Summary: AD patients with a history of recurrent disseminated HSV-1 skin infections form a unique molecular skin endotype group that concurrently exhibits type 2 cytokine, interferon, and IL-36γ-driven skin inflammation, accompanied by dysregulation in expression of epidermal differentiation complex genes involved in barrier function, inflammation, and antimicrobial activity.

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

Skin biopsies are commonly used for the assessment of skin pathology in various skin diseases, including atopic dermatitis (AD). However, because of the invasive nature of skin biopsies, many patients, particularly children, decline participation. This can lead to potential subject sampling bias as data could be skewed toward more severe, older patients who are willing to have biopsies. Recently, researchers have begun studying the skin with a minimal, noninvasive technique using skin tape stripping (STS) to profile the epidermal transcriptome, proteins, and lipids in the skin. However, side-by-side comparisons of skin biopsies with STS have not been done to assess epidermal penetration. Therefore, 20 STS were collected from the volar surface of forearms from healthy nonatopic subjects and patients with AD, following this skin biopsies were collected from adjacent nontaped and taped areas of the skin. Using hematoxylin and eosin staining and immunostaining, we demonstrated that 20 STS reached the upper granular layer of the epidermis. Additionally, we found that the expression of terminal differentiation markers in samples from STS procedure positively correlated with the expression level of these markers in matching skin biopsies. Therefore, STS is a noninvasive and reliable approach to evaluate the expression of skin terminal differentiation markers, which are defective in AD skin.

Minimally invasive skin tape strip RNA sequencing identifies novel characteristics of the type 2-high atopic dermatitis disease endotype.

BACKGROUND: Expression profiling of skin biopsy specimens has established molecular features of the skin in patients with atopic dermatitis (AD). The invasiveness of biopsies has prevented their use in defining individual-level AD pathobiological mechanisms (endotypes) in large research studies. OBJECTIVE: We sought to determine whether minimally invasive skin tape strip transcriptome analysis identifies gene expression dysregulation in AD and molecular disease endotypes. METHODS: We sampled nonlesional and lesional skin tape strips and biopsy specimens from white adult patients with AD (18 male and 12 female patients; age [mean ± SE], 36.3 ± 2.2 years) and healthy control subjects (9 male and 16 female subjects; age [mean ± SE], 34.8 ± 2.2 years). AmpliSeq whole-transcriptome sequencing was performed on extracted RNA. Differential expression, clustering/pathway analyses, immunostaining of skin biopsy specimens, and clinical trait correlations were performed. RESULTS: Skin tape expression profiles were distinct from skin biopsy profiles and better sampled epidermal differentiation complex genes. Skin tape expression of 29 immune and epidermis-related genes (false discovery rate < 5%) separated patients with AD from healthy subjects. Agnostic gene set analyses and clustering revealed 50% of patients with AD exhibited a type 2 inflammatory signature (type 2-high endotype) characterized by differential expression of 656 genes, including overexpression of IL13, IL4R, CCL22, CCR4 (log2 fold change = 5.5, 2.0, 4.0, and 4.1, respectively) and at a pathway level by TH2/dendritic cell activation. Both expression and immunostaining of skin biopsy specimens indicated this type 2-high group was enriched for inflammatory, type 2-skewed dendritic cells expressing FcεRI. The type 2-high endotype group exhibited more severe disease by using both the Eczema Area and Severity Index score and body surface area covered by lesions. CONCLUSION: Minimally invasive expression profiling of nonlesional skin reveals stratification in AD molecular pathology by type 2 inflammation that correlates with disease severity.