Rissmann Robert, Groenink Hendrik W W, Weerheim Arij M, Hoath Steven B, Ponec Maria, Bouwstra Joke A
Department of Drug Delivery Technology, Leiden/Amsterdam Center for Drug Research, Leiden University, Leiden, The Netherlands.
J Invest Dermatol. 2006 Aug;126(8):1823-33. doi: 10.1038/sj.jid.5700305. Epub 2006 Apr 20.
The upper layer of the epidermis, the stratum corneum (SC), is very important for skin barrier function. During the last trimester of gestation, the SC of the fetus is protected by a cheesy, white biofilm called vernix caseosa (VC). VC consists of water-containing corneocytes embedded in a lipid matrix and the basic structure shows certain similarities with the SC. This study aimed to characterize VC, with the main focus on an integral analysis of free and (to the corneocytes) bound lipids, on the lipid organization, and on ultrastructure. Free lipids of VC show a wide distribution in polarity; nonpolar lipids such as sterol esters and triglycerides predominate, having a chain length of up to 32 carbon atoms. The profile of fatty acids, omega-hydroxyacids and omega-hydroxyceramides - representing the bound lipids of VC - shows high similarity to that of SC. Morphological studies revealed the presence of highly hydrated corneocytes embedded in lipids, the latter being occasionally accumulated as lipid pools. Freeze fracture electron microscopy showed smooth surfaces of corneocytes and a heterogeneous appearance of intercellular lipids. The results suggest a lower degree of ordering of VC lipids as compared to the SC. A small-angle X-ray diffraction study showed similar results.
表皮的上层，即角质层（SC），对皮肤屏障功能非常重要。在妊娠晚期，胎儿的角质层由一种乳状白色生物膜保护，称为胎脂（VC）。胎脂由嵌入脂质基质中的含水角质形成细胞组成，其基本结构与角质层有一定相似性。本研究旨在表征胎脂，主要侧重于对游离脂质和（对角质形成细胞）结合脂质进行综合分析、脂质组织分析以及超微结构分析。胎脂中的游离脂质在极性上分布广泛；非极性脂质如甾醇酯和甘油三酯占主导，链长可达32个碳原子。脂肪酸、ω-羟基酸和ω-羟基神经酰胺（代表胎脂的结合脂质）的谱图与角质层高度相似。形态学研究显示存在嵌入脂质中的高度水合角质形成细胞，脂质偶尔会积聚成脂质池。冷冻断裂电子显微镜显示角质形成细胞表面光滑，细胞间脂质外观不均一。结果表明，与角质层相比，胎脂脂质的有序程度较低。小角X射线衍射研究也显示了类似结果。
