Stratum corneum swelling. Biophysical and computer assisted quantitative assessments.

The aim of this study was to characterize the swelling behaviour of the stratum corneum. Stratum corneum pieces isolated from the breast region of 20 different females were incubated in distilled water at two different temperatures (20 degrees C and 45 degrees C) for 90 min and 24 h, respectively. Half of the stratum corneum pieces were previously extracted with chloroform-methanol (2:1). The area-enlargement was photographically recorded. The thickness enlargement was determined using a confocal laser scanning microscope. The average swelling (99% confidence interval) in the area dimension at 20 degrees C was 8.4% +/- 1.4% (n = 20), which corresponded to an average swelling in the length (lateral) dimension of approximately 4.1%. The swelling in the thickness dimension was 26.3% +/- 16.3% (n = 8). The swelling was most pronounced in the thickness dimension and was complete after 90 min of water immersion (P < 0.01, n = 5). In addition, the removal of the intercellular lipids with chloroform/methanol (2:1) induced a decreased swelling in the samples (P < 0.01, n = 20). An increase in temperature of the water from 20 degrees C to 45 degrees C resulted in an increase in swelling (P < 0.01, n = 20). Taken together our results support the idea that the mechanism of stratum corneum swelling is linked to the intercellular lipid structure and hence to skin barrier function.