Raman confocal microscopy and biophysics multiparametric characterization of the skin barrier evolution with age.

Skin aging is a multifactorial phenomenon that involves alterations at the molecular, cellular and tissue levels. Our aim was to carry out a multiparametric biophysical and Raman characterization of skin barrier between individuals of different age groups (<24 and >70 years old). Our results showed a significant decrease of lipids to proteins ratio overall the thickness of the stratum corneum and higher lateral packing in the outer part of the SC for elderly. This can explain the decrease in trans epidermal water loss measured values rather than only SC thickening. Both age groups showed similar water content at SC surface while elderly presented higher water content in deep SC and viable epidermis. Mechanical measurements showed a decrease in the elasticity and an increase in the fatigability with age and were correlated with partially bound water. Highest correlation and anti-correlation values were observed for the deepest part of the SC and the viable epidermis.

Skin surface lipid composition in women: increased 2,3-oxidosqualene correlates with older age.

The importance of the hydrolipidic film of skin has been well documented, however, few data are available in cases of very old age. Our aim was to characterize the difference in skin surface lipid (SSL) composition between individuals of different age groups. Data were collected from the forehead of 22 young volunteers (18-24 years old) and 18 senior volunteers (70-75 years old). The amount of sebum was obtained by sebumetry. To acquire relevant information about the molecular composition of high complex mixtures, SSLs were analysed in a single run to ensure that the lipid structures remain intact, using high-temperature gas chromatography coupled with mass spectrometry. The major features associated with aged skin were documented. In aged skin, a lower sebum content was observed, together with modification of the relative SSL composition involving a significant reduction in the intensity of many components of the hydrolipidic film. In contrast, the intensity of 2,3-oxidosqualene was shown to increase with an inverse relationship between triglycerides and their hydrolytic products. These adaptations could be related to modifications of enzymatic activity.