1. ¹Department of Drug Delivery Technology, Leiden/Amsterdam Center for Drug Research, Leiden University, Leiden, The Netherlands
2. ²Department of Dermatology, Leiden University Medical Center, Leiden, The Netherlands
3. ³Skin Sciences Institute, Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, Ohio, USA

Correspondence: Professor Dr Joke A. Bouwstra, Department of Drug Delivery Technology, Leiden/Amsterdam Center for Drug Research, PO Box 9502, RA Leiden 2300, The Netherlands. E-mail: Bouwstra@chem.leidenuniv.nl

Received 12 December 2005; Revised 23 January 2006; Accepted 10 February 2006; Published online 20 April 2006.

Abstract

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, -hydroxyacids and -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.