Epidermal barrier impairment predisposes for excessive growth of the allergy-associated yeast Malassezia on murine skin

The skin barrier is vital for protection against environmental threats including insults caused by skin-resident microbes. Dysregulation of this barrier is a hallmark of atopic dermatitis (AD) and ichthyosis, with variable consequences for host immune control of colonizing commensals and opportunistic pathogens. While Malassezia is the most abundant commensal fungus of the skin, little is known about the host control of this fungus in inflammatory skin diseases. Here we show that in barrier-impaired skin, Malassezia acquires enhanced fitness and overt growth properties. By using four distinct and complementary murine models of atopic dermatitis and ichthyosis we provide evidence that structural and metabolic changes in the dysfunctional epidermal barrier environment provide increased accessibility and an altered lipid profile, to which the lipid-dependent yeast adapts for enhanced nutrient assimilation. These findings reveal fundamental insights into the implication of the mycobiota in the pathogenesis of common skin barrier disorders. Overall design: Comparative gene expression profiling analysis of RNA-seq data for murine ear skin that was pretreated with MC903 or EtOH (control) for 10 days and associated with Malasseia pachydermatis or olive oil (vehicle) for 4 or 7 days.