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Vernix Caseosa: The Ultimate Natural Cosmetic?
By: Johann W. Wiechers, PhD, JW Solutions; and Bernard Gabard, PhD, Iderma
Posted: August 31, 2009, from the September 2009 issue of Cosmetics & Toiletries.
- Figure 1. Vernix caseosa covers newborn infants
- Figure 2. Lipid, free lipid extract and ceramide analyses
- Figure 3. Water loss profiles
- Figure 4. Water loss profiles of vernix caseosa films as a function of relative humidity
- Figure 5. Equilibrium water sorption-desorption curves
- Figure 6. Percent barrier recovery after tape stripping versus film permeability
- Figure 7. Moisture accumulation assessment
- Figure 8. Water release profiles
- Figure 9. Microgels and coating lipids
- Figure 10. Water release profiles of native VC and various biofilms
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Vernix caseosa Composition: The ‘Inside’ Story
The typical composition of vernix caseosa is 10% lipid, 10% protein and 80% water. The water is mainly present within the keratinocytes as identified with cryo-scanning electron microscopy coupled with X-ray beam analysis.11 Although the protein content is not as well-characterized as its lipid constituents, a plethora of antimicrobial peptides have been recently identified.2, 5, 8, 9 Much more is known about the lipid composition of vernix caseosa. Recent analyses of the lipid constituents have been published12-15 and these results are compared in Table 1 with the typical composition of SC lipids and skin surface lipids, also previously published.12, 14, 15
Table 1 groups together typical skin barrier lipids (ceramides, cholesterol and free fatty acids) as well as those originating from the sebaceous glands. Comparing these groups, one can clearly see that the SC and sebaceous glands produce completely different lipids. However, the lipids found in vernix caseosa are a mixture of skin barrier and sebaceous lipids (also see Table 1). Scientists have used this profile as a way to establish the origin of vernix caseosa. Its high content of squalene and wax esters originally suggested that the lipids in vernix caseosa were derived mainly from fetal sebaceous glands. Stewart et al., for instance, demonstrated in the early 1980s that the lipids in vernix caseosa were most likely derived from the sebaceous gland via the fatty acid composition of wax esters in this biofilm.16 Later studies, however, demonstrated the presence of all major SC lipids in vernix caseosa.12
Hoeger et al.13 refined this picture and demonstrated that the composition pattern of the ceramides found in vernix caseosa mirrored that of mid-gestational fetal epidermis, therefore representing what they called a homologous substitute for the immature epidermal barrier in fetal skin. Combine this with the fact that the periderm, mentioned above, is shed as the fetal sebaceous unit is developing, and this composition is explained.
If all the usual SC lipids including ceramides, cholesterol and free fatty acids are present in vernix caseosa, does this mean that vernix caseosa also fulfills a barrier function for the unborn child? In order to address this question, two other issues must first be addressed. Apart from having ceramides, cholesterol and free fatty acids present, the ceramide profile (i.e., which ceramides are present) and the packing state of the lipids (i.e., how they are grouped) need to meet certain requirements.
Hoeger et al.13 and Rissmann et al.15 both describe the complete ceramide profile of vernix caseosa. Whereas the former states that the ceramide profile is identical to mid-gestational and immature SC of a developing fetus, the latter states that although the levels of ceramides present in mature SC and the vernix caseosa are very different, their profiles are very similar (see Figure 2). Most abundant is CER(AH) at 22.0 ± 6.6% (formerly known as Ceramide 7); followed by slightly lower levels of CER(NS) (Cer 2, 19.5 ± 5.9%); CER(AS/NH) (Cer 5/8, 17.3 ± 3.3%); and CER(EOS) (Cer 1, 14.8 ± 6.0%).