The molecular features of normal and atopic dermatitis skin in infants, children, adolescents, and adults

Background: Although atopic dermatitis (AD) often presents in infancy and persists into adulthood, comparative characterization of AD skin among different pediatric age groups is lacking. Objective: We sought to define skin biopsy profiles of lesional and nonlesional AD across different age groups (0-5-year-old infants with disease duration <6 months, 6-11-year-old children, 12-17-year-old adolescents, >= 18-year-old adults) versus age appropriate controls. Methods: We performed gene expression analyses by RNA-sequencing and real-time PCR (RT-PCR) and protein expression analysis using immunohistochemistry. Results: T(H)2/T(H)22 skewing, including IL-13, CCL17/thymus and activation-regulated chemokine, IL-22, and S100As, characterized the common AD signature, with a global pathway-level enrichment across all ages. Nevertheless, specific cytokines varied widely. For example, IL-33, IL-1RL1/IL-33R, and IL-9, often associated with early atopic sensitization, showed greatest upregulations in infants. T(H)17 inflammation presented a 2-peak curve, with highest increases in infants (including IL-17A and IL-17F), followed by adults. T(H)1 polarization was uniquely detected in adults, even when compared with adolescents, with significant upregulation in adults of IFN-gamma and CXCL9/CXCL10/CXCL11. Although all AD age groups had barrier abnormalities, only adults had significant decreases in filaggrin expression. Despite the short duration of the disease, infant AD presented robust downregulations of multiple barrier-related genes in both lesional and nonlesional skin. Clinical severity scores significantly correlated with T(H)2/T(H)22-related markers in all pediatric age groups. Conclusions: The shared signature of AD across ages is T(H)2/T(H)22-skewed, yet differential expression of specific T(H)2/T(H)22-related genes, other T-H pathways, and barrier-related genes portray heterogenetic, age-specific molecular fingerprints.

Automated summary

The common signature of AD across ages is T(H)2/T(H)22-skewed, but the specific expression of cytokines varies widely. Barrier abnormalities are present in all AD age groups, but significant decreases in filaggrin expression are only seen in adults.