PLASTIC OCCLUSION STRESS TEST AS A MODEL TO INVESTIGATE THE EFFECTS OF SKIN DELIPIDIZATION ON THE STRATUM-CORNEUM WATER-HOLDING CAPACITY IN-VIVO

The purpose of the study was to develop an in vivo model to study the effects of lipid removal on skin barrier. 16 subjects (age 41 +/- 8) were delipidized in vivo on the volar forearm using respectively ether/acetone (EA; 1:1) and chloroform/methanol (CM; 2:1). A third site served as control. Water holding capacity (WHC) was measured according to the plastic occlusion stress test (POST) procedure: the water desorption curve after removal of the occlusion was recorded in terms of skin surface water loss (SSWL) using and evaporimeter for 30 min. In the central part of the evaporation curve (bound water) the CM-treated site is significantly different from control and EA-treated sites (p<0.01). The SSWL decay constants reflecting the desorption rate of water from SC are higher in the CM-treated site (p<0.01). The data are consistent with the effect of CM delipidization (polar lipids) on bound water. No differences are recorded in the evaporation of free water. We conclude that polar lipids have a key role in modulating barrier function and WHC of the stratum corneum. The POST can represent a useful in vivo model to study the effects of lipid extraction on skin function.