The effect of prolonged water exposure on the epidermal permeability barrier

Background: Water exposure is considered an important causative factor of irritant contact dermatitis. It is also known that water exposure can disrupt the stratum corneum (SC). However, there are only a few morphologic studies on the effect of water contact on the skin. Objective: The aim of our study was to investigate the effects of prolonged water exposure on the permeability barrier and the ultrastructure of the SC intercellular lipids. Methods: After prolonged water exposure of hairless mouse skin in vivo for 24, 36, 48, and 72 hrs respectively, the permeability barrier function was assessed by transepidermal water loss (TEWL) measurement, and the ultra-structure of SC by electron microscopy using osmium tetraoxide and ruthenium tetraoxide postfixation and calcium ion capture cytochemistry. Additionally, the lipid composition was evaluated using confocal microscopy with nile red stain and the integrity of the SC assessed using a lanthanum tracer. Results: After prolonged water exposure, water caused a significant increase in TEWL with disappearance of the calcium gradient, but this did not significantly influence the recovery rate of TEWL. The intercellular lipids were disrupted, and multiple lacunae containing abnormal delaminated materials within the intercellular spaces were observed. Lanthanum tracer penetrated into the intercellular space of the SC. There was a progressive decrease in nile red staining with neutral lipid content. With increasing exposure to water, these results were more evident. Conclusion: Our results provide a better understanding of the disruptive effect of prolonged water exposure on barrier lipids, the penetration-enhancing effect of water and the increased susceptibility to irritants, with regard to duration of water exposure.