Low Humidity Alters Epidermal Gene Expression in vivo

Introduction: Environmental factors, including humidity, affect cutaneous functions. The influences of low humidity on epidermal gene expression and whether an emollient can attenuate its effects are unknown. Methods: We employed RNAseq technique to analyze epidermal gene expression in mice exposed to low humidity (15%) with or without topical treatment with an emollient (Dr. Yu Skin Barrier Repair Cream ® ) for 6 months. Mice maintained in normal humidity (55± 5%) served as normal controls. Results: Exposure of mice to low humidity down-regulated 159 genes and upregulated 105 genes in the epidermis. Topical applications of the emollient upregulated 195 genes and downregulated 280 genes in mice exposed to low humidity. Low humidity primarily downregulated genes associated with interaction between viral proteins and cytokines, and cytokine-cytokine interaction pathways, while upregulating genes associated with IL-17 and TNF signaling pathways. Topical emollient upregulated signaling pathways associated with fatty acid elongation, peroxisome proliferator-activated receptors (PPAR) and fatty acid metabolism in mice exposed to low humidity, while down-regulated genes were associated with inflammation. Conclusion: These results demonstrate that low humidity alters epidermal gene expression, and topical emollient regulates epidermal gene expression in mice exposed to low humidity, providing a rationale for utility of emollients in low-humidity environment and the management of dry skin. Keywords: environment, humidity, epidermis, emollient, RNA sequencing, cytokines