Synchronized in vivo measurements of skin hydration and trans-epidermal water loss. Exploring their mutual influences.

OBJECTIVE: To explore the relationship between skin surface hydration and Trans-Epidermal Water Loss (TEWL) when simultaneously measured. METHODS: Six circular skin areas of the forearms (3 per forearm, 3 cm in diameter) of 12 Caucasian women were used as models. 4 prototypes of formulae of different compositions containing glycerol at different concentrations 7%, 10% and 40% were used as models of hydrating products. One formula (glycerol-free) was used as control vehicle. Standardized applications of formulae (2 mg/cm2 ) were performed on 5 skin sites chosen at random, the other being left as bare/control. A recently marketed instrumental device that records the skin surface hydration and TEWL on a small skin area in a simultaneous manner was used. Measurements were carried out at T0 (pre-application), at 1 h (T1) and 5 h (T5) post applications on two close sites within the 6 defined areas of both forearms. RESULTS: The new instrumental device allowed to clearly differentiate the 5 formulae (i.e. 7% vs. 10%) with regard the dose effect brought by glycerol (7%, 10%, 40%) and to record their lingering effects at T1 and T5. Both parameters were found significantly and negatively correlated, i.e. the higher the skin hydration, the lower the TEWL. The 40% concentration of glycerol, that leads to the highest skin hydration, brings a drop in the TEWL by about a two-fold factor. Skin hydration of bare skin and control/vehicle sites showed minor and non-significant changes along 5 h. Instead, the control/ vehicle slowed down the TEWL to a slight extent. CONCLUSION: The use of this new instrumental device shed a new light on the mutual and inverse relationships between skin hydration and TEWL. Results suggest that, at high concentration, glycerol leads to largely increase the water content of both epidermal and dermal compartments, possibly leading to structural changes in the skin relief.

OBJECTIF: D'explorer les relations mutuelles entre l'hydratation cutanée et la perte insensible en eau (PIE) quand elles sont mesurées simultanément. MÉTHODES: 6 zones circulaires des avant-bras (3 par zone, diamètre 3 cm) de 12 femmes Caucasiennes ont été utilisées comme modèles. 4 prototypes de formules, de compositions différentes contenant du glycérol à différentes concentrations (7%, 10%, 40%) furent réalisés et utilisés comme modèles de produits hydratants. Une formule sans glycérol fut utilisée en tant que contrôle. Des applications standardisées (2 mg/cm2 ) ont été effectuées sur 5 zones de façon aléatoire, la sixième restant nue en tant que contrôle. Un appareil nomade récemment disponible sur le marché qui enregistre l'hydratation et la PIE simultanément sur une petite surface cutanée a été utilisé. Deux mesures à deux endroits voisins de chaque zone ont été conduites à T0 (avant applications), 1 heure (T1) et 5 heures (T5) après. RÉSULTATS: Ce nouvel instrument permet de clairement différencier les 5 formules dans l'effet dose apporté par le glycérol (0, 7%, 10%, 40%) et de suivre leur rémanence dans le temps (T5 vs. T1). Les deux paramètres ont été trouvés négativement corrélés de manière significative, c'est-à-dire qu'une plus forte hydratation correspondant à une plus faible PIE. La formule à 40% de glycérol, qui a conduit à la plus forte hydratation, a ainsi entrainé une chute de la PIE d'environ 50%. La peau nue comme celle de la formule contrôle n'ont pas conduit à de modifications notables et significatives de l'hydratation. La formule contrôle a conduit à une légère chute de la PIE. CONCLUSION: L'utilisation de ce nouvel instrument semble apporter un éclairage nouveau sur les relations mutuelles (et inverses) entre l'hydratation cutanée et la PIE. Les résultats suggèrent qu'à forte concentration, le glycérol conduit à un fort accroissement de la teneur en eau de l'épiderme et du derme, avec de possibles conséquences structurelles du relief cutané.

Anatomy and physiology of subcutaneous adipose tissue by in vivo magnetic resonance imaging and spectroscopy: relationships with sex and presence of cellulite.

BACKGROUND: Little is still known concerning subcutaneous adipose tissue and cellulite, and controversial questions are still under discussion. AIMS: Magnetic resonance imaging and spectroscopy were used to address two unresolved questions relating to the anatomy and physiology of subcutaneous adipose tissue. METHODS: Using high spatial resolution magnetic resonance imaging we characterized the topography of the dermo- hypodermal junction, and the three-dimensional architecture of the subcutaneous fibrous septae. Using proton spectroscopy, we measured water and lipid fractions within a fat lobule, and T1 and T2 values of the detected compounds. All these data were analysed according to sex and presence of cellulite. RESULTS: MR imaging quantified deeper indentations of adipose tissue into the dermis, and evidenced for the first time a great increase in the thickness of the inner fat layer in women with cellulite. Moreover, 3D reconstruction of the fibrous septae network showed a higher percentage of septae in a direction perpendicular to the skin surface in women with cellulite; but our study also depicted the tortuous aspect of this network. MR proton spectroscopy could not show any differences related to sex or presence of cellulite concerning T1 and T2 relaxation times of the detected compounds within a fat lobule, neither the unsaturated lipid fraction, the saturated lipid fraction, nor the water fraction. CONCLUSIONS: Magnetic resonance imaging showed that the 3D architecture of fibrous septae couldn't be modelled simply as perpendicular planes for women and tilted planes at 45 degrees for men. MR spectroscopy did not confirm the hypothesis of increased water content in the adipose tissue of women with cellulite as suggested by others, except if such water would be located in the connective septae.