Pickens W L, Warner R R, Boissy Y L, Boissy R E, Hoath S B
The Skin Sciences Institute and Division of Neonatology, Children's Hospital Medical Center, Cincinnati, Ohio, USA.
J Invest Dermatol. 2000 Nov;115(5):875-81. doi: 10.1046/j.1523-1747.2000.00134.x.
Recent studies have prompted interest in the use of epidermal barrier creams as protective biofilms for very low birthweight preterm infants. The key to understanding the role of epidermal barrier films is an elucidation of their interaction with water and a basic knowledge of their composition. In this study, we investigated the morphologic properties and elemental composition of the naturally occurring biofilm, vernix caseosa. This biofilm is typically lacking in preterm infants and its production coincides in utero with terminal differentiation of the epidermis and formation of the stratum corneum. Significantly, vernix (80.5+/-1.0% H2O) had a much higher water content than other barrier creams (Eucerin: 17.1+/-0.6%, Aquaphor: 0.33+/-0.03%, Ilex: 0.19+/-0.02%, petrolatum: 0.03+/-0.01%; all p<0.05). Phase contrast microscopy of vernix showed multiple cellular elements with nucleic "ghosts" embedded in a putative lipid matrix. Transmission electron microscopy revealed flattened structures approximately 1-2 microm in thickness with distinct cellular envelopes indicative of differentiated corneocytes. Compared with mature corneocytes in adult stratum corneum, vernix corneocytes appeared swollen, the density of the keratin filaments was less, and there was a relative lack of tonofilament orientation. Cryofractured specimens were examined by cryoscanning electron microscopy with subsequent elemental localization by X-ray beam analysis. The findings indicate the high water content of vernix is largely compartmentalized within fetal corneocytes. These results are consistent with the novel view of vernix as a "fluid phase" stratum corneum consisting of a hydrophobic lipid matrix with embedded fetal corneocytes possessing unique biomechanical and water-binding properties.
最近的研究引发了人们对使用表皮屏障乳膏作为极低出生体重早产儿保护性生物膜的兴趣。理解表皮屏障膜作用的关键在于阐明它们与水的相互作用以及对其成分的基本知识。在本研究中，我们调查了天然存在的生物膜——胎脂的形态学特性和元素组成。这种生物膜在早产儿中通常缺乏，其产生与子宫内表皮的终末分化和角质层的形成同时发生。值得注意的是，胎脂（80.5±1.0%水）的含水量比其他屏障乳膏高得多（优色林：17.1±0.6%，凡士林：0.33±0.03%，冬青油：0.19±0.02%，凡士林：0.03±0.01%；所有p<0.05）。胎脂的相差显微镜显示多个细胞成分，有核“幽灵”嵌入假定的脂质基质中。透射电子显微镜显示扁平结构，厚度约为1 - 2微米，有明显的细胞包膜，表明是分化的角质形成细胞。与成人角质层中的成熟角质形成细胞相比，胎脂角质形成细胞显得肿胀，角蛋白丝的密度较小，并且相对缺乏张力丝的定向。通过低温扫描电子显微镜检查冷冻断裂标本，随后通过X射线束分析进行元素定位。研究结果表明，胎脂的高含水量在很大程度上被分隔在胎儿角质形成细胞内。这些结果与将胎脂视为由疏水脂质基质和具有独特生物力学和水结合特性的嵌入胎儿角质形成细胞组成的“液相”角质层的新观点一致。
