EXPOSURE TO A DRY ENVIRONMENT ENHANCES EPIDERMAL PERMEABILITY BARRIERFUNCTION

Previous studies have suggested that transepidermal water movement may play an important role in epidermal homeostasis and barrier repair. H ere we analyzed cutaneous barrier function, epidermal morphology, and lipid content of the stratum corneum in hairless mice maintained in a high relative humidity (RH > 80%) versus low humidity (RH < 10%) envir onment for 2 wk. Basal transepidermal water loss was reduced by 31% in animals maintained in a dry venus humid environment. Moreover, the nu mber of lamellar bodies in stratum granulosum cells, the extent of lam ellar body exocytosis, and the number of layers of stratum corneum inc reased in animals kept in a dry environment. Furthermore, the dry weig ht of the stratum corneum and the thickness of the epidermis also incr eased in a dry environment. in addition, total stratum corneum lipids increased but lipid analysis revealed no significant differences in li pid distribution. Lastly, barrier recovery following either acetone tr eatment Or tape stripping was accelerated after prolonged prior exposu re to a dry environment, while conversely, it was delayed by prior exp osure to a humid environment. These studies demonstrate that environme ntal conditions markedly influence epidermal structure and function, a nd suggest mechanisms by which the environment could induce or exacerb ate various cutaneous disorders.