ABSTRACT
The skin of the third trimester fetus and early newborn exhibits a complex, multifunctional, highly hydrated but viscous skin-surface biofilm called vernix caseosa (VC). During birth, VC undergoes a substantial change from an aqueous and warm surrounding into a gaseous and colder environment postnatally. The aim of this study was to investigate the structural and physicochemical changes in VC, which accompany physiologically relevant variations in environment parameters, such as temperature and humidity. A remarkable difference was observed in water release and uptake properties: dehydration and rehydration processes take place two to four times faster at 37 degrees C than at room temperature (RT). The dehydration was irreversible; rehydration was only possible to a final weight of 55% (37 degrees C) and 46% (RT) of the pre-desiccation weight. Differential scanning calorimetry showed two different overlapping phase transitions within physiological temperature range. Investigation of the lipid organization by Fourier transform infrared spectroscopy and small-angle X-ray diffraction revealed a more disordered state of lipids at 37 degrees C than at RT, which might explain the faster dehydration and rehydration process at 37 degrees C as well as the changes in thermotropic rheological behavior. In conclusion, we demonstrated that VC properties adjust to the fundamental change from the intrauterine to the post-natal environment.
Subject(s)
Adaptation, Physiological/physiology , Temperature , Vernix Caseosa/cytology , Vernix Caseosa/physiology , Water/metabolism , Calorimetry, Differential Scanning , Desiccation , Elasticity , Humans , Humidity , Infant, Newborn , Lipid Metabolism , Microscopy, Electron, Scanning , Rheology , Skin Physiological Phenomena , Spectroscopy, Fourier Transform Infrared , Viscosity , X-Ray DiffractionABSTRACT
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.
