Background: Modelling atopic dermatitis (AD) in vitro is paramount to understand the disease pathophysiology and identify novel treatments. Previous studies have shown that the Th2 cytokines IL-4 and IL-13 induce AD-like features in keratinocytes in vitro. However, it has not been systematically researched whether the addition of Th2 cells, their supernatants or a 3D structure are superior to model AD compared to simple 2D cell culture with cytokines. Methods: For the first time, we investigated what in vitro option most closely resembles the disease in vivo based on single-cell RNA sequencing data (scRNA-seq) obtained from skin biopsies in a clinical study and published datasets of healthy and AD donors. In vitro models were generated with primary fibroblasts and keratinocytes, subjected to cytokine treatment or Th2 cell cocultures in 2D/3D. Gene expression changes were assessed using qPCR and Multiplex Immunoassays. Results: Of all cytokines tested, incubation of keratinocytes and fibroblasts with IL-4 and IL-13 induced the closest in vivo-like AD phenotype which was observed in the scRNA-seq data. Addition of Th2 cells to fibroblasts failed to model AD due to the downregulation of ECM-associated genes such as POSTN. While keratinocytes cultured in 3D showed better stratification than in 2D, changes induced with AD triggers did not better resemble AD keratinocyte subtypes observed in vivo. Conclusions: Taken together, our comprehensive study shows that the simple model using IL-4 or IL-13 in 2D most accurately models AD in fibroblasts and keratinocytes in vitro, which may aid the discovery of novel treatment options.

Background: Atopic dermatitis (AD) is a chronic inflammatory skin disease caused by skin barrier defects and a misdirected type 2 immune response against antigens. The skin microbiome in AD is characterised by a reduction in microbial diversity with a dominance of staphylococci, including Staphylococcus epidermidis (S. epidermidis). To assess whether S. epidermidis antigens play a role in AD, we studied the immune response against the extracellular serine protease (Esp). Methods: We analyzed the binding of human IgG4 to S. epidermidis extracellular proteins using immunoblotting and mass spectrometry. We then measured serum antibodies specific for recombinant Esp by ELISA in healthy and AD individuals. We also stimulated T cells from AD patients and control subjects with Esp and measured the secreted cytokines. Finally, we analyzed the proteolytic activity of Esp against IL-33 and determined the cleavage sites by mass spectrometry. Results: We identified Esp as the dominant IgG4-binding antigen of S. epidermidis. Esp-specific IgE was present in human serum; AD patients had higher concentrations than controls. The T cell response to Esp in healthy adults was characterized by IL-17, IL-22, IFN-γ, and IL-10, whereas the AD patients’ T cells lacked IL-17 production and released only low amounts of IL-22, IFN-γ, and IL-10. In contrast, Th2 cytokine release was higher in T cells from AD patients than from healthy controls. Mature Esp cleaved and activated the alarmin IL-33. Conclusions: Esp elicits type 2-biased response in AD patients. This suggests that S. epidermidis can aggravate AD through the allergenic properties of Esp.

Atopic dermatitis (AD) is a common skin disease during infancy, which imposes a considerable burden on patients, their families, and the society, requiring effective treatment options that result in rapid and sustained symptom relief. Additionally, early treatment may prevent the development of atopic comorbidities by restoring the skin barrier. Currently, topical standard-of-care for AD in infants includes emollients and topical corticosteroids (TCS) to treat and reduce the risk of flares. However, only few have been approved for infants and long-term maintenance therapy with TCS is not indicated due to potential local and systemic side effects, including skin atrophy. Accordingly, the recently updated European guidelines for treatment of AD recommend topical calcineurin inhibitors (TCIs) for long-term use, treatment of sensitive skin areas, and for use in the pediatric population. Evidence on the use of TCIs for infants has almost been exclusively collected for pimecrolimus, with >4,000 infants evaluated in clinical trials, consistently confirming that pimecrolimus is a safe and effective treatment for infants with AD. Nevertheless, its use is still restricted in most countries to children above the age of 2 years due to initial and mostly theoretical safety concerns. Based on a careful review of the available evidence of clinical trials, post-marketing surveillance, and epidemiological studies, an Expert Panel of European dermatologists and pediatric allergologists concluded that these safety concerns are no longer valid. Therefore, pimecrolimus offers a safe and effective alternative to TCS in infants aged 3 months and above, and labeling restrictions in this age group are no longer justified.

This systematic review evaluates the efficacy, safety and economic impact of dupilumabcompared to standard of care for uncontrolled moderate-to-severe atopic dermatitis (AD). Pubmed, EMBASE and Cochrane Library were searched for RCTs and health economic evaluations. Critical and important AD-related outcomes were considered. The risk of bias and the certainty of the evidence were assessed using GRADE. Seven RCTs including 1845 subjects > 12 years treated with dupilumab16 to 52 weeks were evaluated. For adultsthere is high certainty that dupilumabdecreasesSCORAD (MD -30,72; 95%CI -34,65% to -26,79%) and EASI-75 (RR 3.09; 95%CI 2.45 to 3.89), pruritus (RR 2.96; 95%CI 2.37 to 3.70), rescue medication (RR 3.46; 95%CI 2.79 to 4.30), sleep disturbance (MD -7.29; 95%CI -8.23 to -6.35), anxiety/depression (MD -3.08; 95% CI -4.41 to -1.75) and improves quality of life (MD -4.80; 95% CI -5.55 to -4.06). The efficacy for adolescents is similar. Dupilumab-related adverse events (AEs) slightly increase (low certainty). The evidence for dupilumab-related serious AE is uncertain. The incremental cost-effectiveness ratio ranged from 28,500 £ (low certainty) to 124,541 US$ (moderate certainty).More data on long term safety are needed both for children and adults, together with more efficacy data in the paediatric population.

This systematic review evaluates the efficacyand safety of omalizumab for chronic spontaneous urticaria (CSU). Pubmed, EMBASE and Cochrane Library were searched for RCTs. Critical and important CSU-related outcomes were considered. The risk of bias and the certainty of the evidence were assessed using GRADE. Ten RCTs including 1620 subjects aged 12 to 75 years old treated with omalizumab for 16 to 40 weeks were evaluated. Omalizumab 150 mg: does not result in clinically meaningful improvement(high certainty) of the urticaria activity score (UAS)7 (mean difference (MD) -5; 95%CI -7.75 to -2.25) and the itch severity score(ISS)7 (MD -2.15; 95% CI -3.2 to -1.1); does not increase (moderate certainty) quality of life (QoL) (Dermatology Life Quality Index (DLQI); MD -2.01; 95%CI -3.22 to -0.81); decreases (moderate certainty) rescue medication use (MD -1.68; 95%CI -2.95 to -0.4). Omalizumab 300 mg:results in clinically meaningful improvements(moderate certainty)of the UAS7 (MD -11.05; 95%CI -12.87 to -9.24), theISS7 (MD -4.45; 95%CI -5.39 to -3.51), and QoL (high certainty)(DLQI; MD -4.03; 95% CI -5.56 to -2.5); decreases (moderate certainty) rescue medication use (MD -2.04; 95%CI -3.19 to -0.88) and drug-related serious AEs (RR 0.77; 95%CI 0.20 to 2.91).