Major differences between human atopic dermatitis and murine models, as determined by using global transcriptomic profiling.

BACKGROUND: Atopic dermatitis (AD) is caused by a complex interplay between immune and barrier abnormalities. Murine models of AD are essential for preclinical assessments of new treatments. Although many models have been used to simulate AD, their transcriptomic profiles are not fully understood, and a comparison of these models with the human AD transcriptomic fingerprint is lacking. OBJECTIVE: We sought to evaluate the transcriptomic profiles of 6 common murine models and determine how they relate to human AD skin. METHODS: Transcriptomic profiling was performed by using microarrays and quantitative RT-PCR on biopsy specimens from NC/Nga, flaky tail, Flg-mutated, ovalbumin-challenged, oxazolone-challenged, and IL-23-injected mice. Gene expression data of patients with AD, psoriasis, and contact dermatitis were obtained from previous patient cohorts. Criteria of a fold change of 2 or greater and a false discovery rate of 0.05 or less were used for gene arrays. RESULTS: IL-23-injected, NC/Nga, and oxazolone-challenged mice show the largest homology with our human meta-analysis-derived AD transcriptome (37%, 18%, 17%, respectively). Similar to human AD, robust TH1, TH2, and also TH17 activation are seen in IL-23-injected and NC/Nga mice, with similar but weaker inflammation in ovalbumin-challenged mice. Oxazolone-challenged mice show a TH1-centered reaction, and flaky tail mice demonstrate a strong TH17 polarization. Flg-mutated mice display filaggrin downregulation without significant inflammation. CONCLUSION: No single murine model fully captures all aspects of the AD profile; instead, each model reflects different immune or barrier disease aspects. Overall, among the 6 murine models, IL-23-injected mice best simulate human AD; still, the translational focus of the investigation should determine which model is most applicable.

Identification of novel immune and barrier genes in atopic dermatitis by means of laser capture microdissection.

BACKGROUND: The molecular signature of atopic dermatitis (AD) lesions is associated with TH2 and TH22 activation and epidermal alterations. However, the epidermal and dermal AD transcriptomes and their respective contributions to abnormalities in respective immune and barrier phenotypes are unknown. OBJECTIVE: We sought to establish the genomic profile of the epidermal and dermal compartments of lesional and nonlesional AD skin compared with normal skin. METHODS: Laser capture microdissection was performed to separate the epidermis and dermis of lesional and nonlesional skin from patients with AD and normal skin from healthy volunteers, followed by gene expression (microarrays and real-time PCR) and immunostaining studies. RESULTS: Our study identified novel immune and barrier genes, including the IL-34 cytokine and claudins 4 and 8, and showed increased detection of key AD genes usually undetectable on arrays (ie, IL22, thymic stromal lymphopoietin [TSLP], CCL22, and CCL26). Overall, the combined epidermal and dermal transcriptomes enlarged the AD transcriptome, adding 674 upregulated and 405 downregulated differentially expressed genes between lesional and nonlesional skin to the AD transcriptome. We were also able to localize individual transcripts as primarily epidermal (defensin, beta 4A [DEFB4A]) or dermal (IL22, cytotoxic T-lymphocyte antigen 4 [CTLA4], and CCR7) and link their expressions to possible cellular sources. CONCLUSIONS: This is the first report that establishes robust epidermal and dermal genomic signatures of lesional and nonlesional AD skin and normal skin compared with whole tissues. These data establish the utility of laser capture microdissection to separate different compartments and cellular subsets in patients with AD, allowing localization of key barrier or immune molecules and enabling detection of gene products usually not detected on arrays.

RNA sequencing atopic dermatitis transcriptome profiling provides insights into novel disease mechanisms with potential therapeutic implications.

BACKGROUND: Genomic profiling of lesional and nonlesional skin of patients with atopic dermatitis (AD) using microarrays has led to increased understanding of AD and identification of novel therapeutic targets. However, the limitations of microarrays might decrease detection of AD genes. These limitations might be lessened with next-generation RNA sequencing (RNA-seq). OBJECTIVE: We sought to define the lesional AD transcriptome using RNA-seq and compare it using microarrays performed on the same cohort. METHODS: RNA-seq and microarrays were performed to identify differentially expressed genes (criteria: fold change, ≥ 2.0; false discovery rate ≤ 0.05) in lesional versus nonlesional skin from 18 patients with moderate-to-severe AD, with real-time PCR (RT-PCR) and immunohistochemistry used for validation. RESULTS: Both platforms showed robust disease transcriptomes and correlated well with RT-PCR. The common AD transcriptome identified by using both techniques contained 217 genes, including inflammatory (S100A8/A9/A12, CXCL1, and 2'-5'-oligoadenylate synthetase-like [OASL]) and barrier (MKi67, keratin 16 [K16], and claudin 8 [CLDN8]) AD-related genes. Although fold change estimates determined by using RNA-seq showed somewhat better agreement with RT-PCR (intraclass correlation coefficient, 0.57 and 0.70 for microarrays and RNA-seq vs RT-PCR, respectively), bias was not eliminated. Among genes uniquely identified by using RNA-seq were triggering receptor expressed on myeloid cells 1 (TREM-1) signaling (eg, CCL2, CCL3, and single immunoglobulin domain IL1R1 related [SIGIRR]) and IL-36 isoform genes. TREM-1 is a surface receptor implicated in innate and adaptive immunity that amplifies infection-related inflammation. CONCLUSIONS: This is the first report of a lesional AD phenotype using RNA-seq and the first direct comparison between platforms in this disease. Both platforms robustly characterize the AD transcriptome. Through RNA-seq, we unraveled novel disease pathology, including increased expression of the novel TREM-1 pathway and the IL-36 cytokine in patients with AD.

Calcipotriol/Betamethasone Dipropionate Foam Inhibits Th17 Cytokine Secretion and Improves Epidermal Barrier Markers in a Human Th17 Skin Inflammation Model.

INTRODUCTION: T-helper 17 (Th17) cytokines play a key role in the pathophysiology of psoriasis by driving inflammatory responses that lead to epidermal alterations. Markers of epidermal differentiation, including the proteins loricrin (LOR), filaggrin (FLG) and involucrin (IVL), are dysregulated in psoriatic skin. The fixed-dose combination of calcipotriol/betamethasone dipropionate (Cal/BD) foam and clobetasol propionate (CP) are widely used, effective topical treatments for psoriasis. In this study, we investigated the effects of Cal/BD foam and CP cream on Th17 cytokine secretion and epidermal differentiation using a human Th17 skin inflammation model (InflammaSkin®). METHODS: The fixed-dose combination Cal/BD foam and the CP cream were applied once and twice daily, respectively, onto the air-exposed epidermal surface of InflammaSkin cultures for 7 days. Th17 cytokine levels were measured in culture supernatants, and gene expression analysis and immunohistochemical staining for LOR, FLG and IVL were performed on the skin samples. RESULTS: Topical treatment with Cal/BD foam almost completely inhibited Th17 cytokine secretion and upregulated LOR and IVL expression, but not FLG expression, at the mRNA and protein levels. Topical treatment with CP cream significantly reduced Th17 cytokine levels, but to a lesser extent than Cal/BD foam, and did not improve expression of any of the epidermal differentiation markers. CONCLUSION: Compared with CP treatment, the fixed-dose combination Cal/BD foam showed a greater suppression of Th17 cytokine secretion and improved epidermal differentiation, resulting in an overall higher degree of improvement of the skin. These results support our understanding of the mechanisms behind the clinical efficacy observed for Cal/BD foam and of its use for long-term proactive treatment of psoriasis vulgaris.

Meta-analysis derived atopic dermatitis (MADAD) transcriptome defines a robust AD signature highlighting the involvement of atherosclerosis and lipid metabolism pathways.

BACKGROUND: Atopic dermatitis (AD) is a common inflammatory skin disease with limited treatment options. Several microarray experiments have been conducted on lesional/LS and non-lesional/NL AD skin to develop a genomic disease phenotype. Although these experiments have shed light on disease pathology, inter-study comparisons reveal large differences in resulting sets of differentially expressed genes (DEGs), limiting the utility of direct comparisons across studies. METHODS: We carried out a meta-analysis combining 4 published AD datasets to define a robust disease profile, termed meta-analysis derived AD (MADAD) transcriptome. RESULTS: This transcriptome enriches key AD pathways more than the individual studies, and associates AD with novel pathways, such as atherosclerosis signaling (IL-37, selectin E/SELE). We identified wide lipid abnormalities and, for the first time in vivo, correlated Th2 immune activation with downregulation of key epidermal lipids (FA2H, FAR2, ELOVL3), emphasizing the role of cytokines on the barrier disruption in AD. Key AD "classifier genes" discriminate lesional from nonlesional skin, and may evaluate therapeutic responses. CONCLUSIONS: Our meta-analysis provides novel and powerful insights into AD disease pathology, and reinforces the concept of AD as a systemic disease.