Imokawa G, Kuno H, Kawai M
Tochigi Research Laboratory, Kao Corporation, Japan.
J Invest Dermatol. 1991 Jun;96(6):845-51. doi: 10.1111/1523-1747.ep12474562.
Stratum corneum lipids have been found to be an important determinant involved in the water-holding function of the stratum corneum. In order to further elucidate the significance of stratum corneum lipids in the water-holding properties, the hydration behavior of the stratum corneum following depletion and replenishment of the lipids has been studied, using an isolated human forearm stratum corneum sheet, by differential scanning calorimetry parallel to ultrastructural changes of intercellular lipids in the stratum corneum. Extraction of the stratum corneum sheet with acetone/ether (1/1) decreased the bound-water content from 33.3% to 19.7%, where the melting temperature of ice remained constant. Further extraction with water, which released a large amount of water-soluble materials such as amino acids, did not change the bound-water content, but definitely raised the melting temperature of ice. The application of the stratum corneum lipids, which were solubilized in squalane containing 1% alpha-monomethyl heptadecyl glyceryl ether to the lipid-depleted stratum corneum sheet, caused a significant recovery of bound-water content to the previous, almost normal level. In accordance with the hydration behavior, electron microscopic analysis of the acetone/ether-treated stratum corneum sheet revealed selective depletion of lipids from the intercellular spaces, accompanied by a marked disruption of multiple lamellar structures. In contrast, the application of stratum corneum lipids into the lipid-depleted stratum corneum sheet resulted in the restoration of the lamellar structure between the stratum corneum cells. These findings strongly suggest that stratum corneum lipids serve a water-holding function through the formation of lamellar structures within the stratum corneum.
角质层脂质已被发现是参与角质层持水功能的一个重要决定因素。为了进一步阐明角质层脂质在持水特性中的重要性，利用分离的人前臂角质层薄片，通过差示扫描量热法并结合角质层细胞间脂质的超微结构变化，研究了脂质耗尽和补充后角质层的水合行为。用丙酮/乙醚（1/1）提取角质层薄片会使结合水含量从33.3%降至19.7%，此时冰的熔化温度保持不变。用水进一步提取，释放出大量水溶性物质如氨基酸，并未改变结合水含量，但确实提高了冰的熔化温度。将溶解在含有1%α-单甲基十七烷基甘油醚的角鲨烷中的角质层脂质应用于脂质耗尽的角质层薄片，会使结合水含量显著恢复到之前几乎正常的水平。根据水合行为，对经丙酮/乙醚处理的角质层薄片进行电子显微镜分析发现，细胞间空间的脂质被选择性耗尽，同时多层结构明显破坏。相反，将角质层脂质应用于脂质耗尽的角质层薄片会导致角质层细胞间的层状结构恢复。这些发现有力地表明，角质层脂质通过在角质层内形成层状结构来发挥持水功能。
