Jean de Rigal

Age-Related Mechanical Properties of Human Skin : An In Vivo Study

We have investigated in vivo how various viscoelastic parameters that describe the mechanical properties of the human skin may vary with age. Accordingly, we have used a mechanical device that records the torsional extensibility of the skin. When submitted to a low torque, the time-response curve of the skin affords the determination of the immediate extensibility (UE), the immediate recovery (UR), the viscoelastic part of the deformation (UV), the elastic recovery (UR/UE), and the creep relaxation time (tau). Because the skin thickness varies with age and primarily governs the mechanical properties, it was measured through an ultrasound technique at the same sites (forearm) where the torque was applied. The results show that the skin maintains its thickness and extensibility up to the seventh decade as opposed to its elasticity or recovery capacities, which decrease from an early age. The viscous part of the deformation is constant through life, whereas the creep relaxation time decreases linearily with age. Except for skin thickness, no differences in these parameters between men and women were detected. The significance of these results are discussed in terms of structure alterations. The determination of the elastic recovery (UR/UE) appears to be a parameter of choice for illustrating skin aging.

The effects of aging on the cutaneous microvasculature

BACKGROUND Few studies have attempted to quantitatively assess in vivo changes in the microvasculature with age. OBJECTIVE The objective was to assess in vivo structural and functional changes in the cutaneous microvasculature with aging and to analyze the contribution of the microvasculature to skin color. METHODS Video capillaroscopy, in conjunction with fluorescein angiography, and laser-Doppler flowmetry were used to compare elderly and young normal volunteers. Skin color differences were assessed with a handheld color reflectance meter. A photoexposed site, the forehead, and the relatively photoprotected ventral forearm were studied to differentiate photoaging from chronologic aging. RESULTS Dermal papillary loops were significantly reduced in old skin compared with young skin (forehead by 40%; forearm by 37%). Horizontal vessels showed increased volume fraction in elderly forehead and forearm skin. Laser-Doppler studies demonstrated no significant differences between young and old skin; indeed, hyperemic responsiveness appeared more rapid in the elderly. Color measurements showed elderly skin, particularly in men, to be significantly darker and redder. CONCLUSION A marked loss in dermal nutritional vessel density and surface area for exchange is a feature of both chronologic aging and photoaging.

MEXORYL SX : A BROAD ABSORPTION UVA FILTER PROTECTS HUMAN SKIN FROM THE EFFECTS OF REPEATED SUBERYTHEMAL DOSES OF UVA

There is now considerable evidence that chronic UVA exposure induces damage in animal and human skin; however, little is known about UVA protection of human skin. The aim of this study is to evaluate the efficacy of Mexoryl SX, a broad UVA absorber (lamada max = 345 nm) against UVA-induced changes in human skin. The regimen of UVA exposure (13 weeks with increasing suberythemal doses) induces intense pigmentation with no erythema. Skin hydration and elasticity decrease, whereas total skin thickness, assessed by echography, remains unchanged. Irradiated epidermis reveals a significant thickening of the stratum corneum, an absence of hyperplasia and an increase in the expression of the protective iron-storage protein ferritin. No significant alterations are seen using antisera against type IV collagen or laminin, suggesting that the dermal-epidermal junction (DEJ) is mainly preserved. In dermis, enhanced expression of tenascin is seen just below the DEJ but type I procollagen, which is localized at the same site, is unaltered. Although we are unable to visualize any changes in elastic network organization using Luna staining or specific antiserum directed against human elastin, we notice an increased deposition of lysozyme or alpha-1 antitrypsin on elastin fibres. Mexoryl SX (5%) efficiently prevents these alterations. Thus, these results suggest that UVA photoprotection can prevent early putative alterations leading to photoageing.

Comparative study of the hydration of the stratum corneum between four ethnic groups: influence of age

Background  Several recent overviews have reported that significant work remains to be performed to understand and quantify the ethnic differences in skin properties.

Skin from various ethnic origins and aging: an in vivo cross-sectional multimodality imaging study

Background: Ethnic differences in skin structural features have not been thoroughly investigated, and the few reported studies are contradictory. Thus, we have carried out a set of in vivo measurements on the skin of about 400 volunteers from various ethnic origins living in the same environment.

The effect of age on skin color and color heterogeneity in four ethnic groups

Background: Few comparative data are available on age‐related changes in skin color among different ethnic groups. The aim of the study was to measure and analyze the skin color and color heterogeneity in four different ethnic groups living in the same local environment and to determine the effects of age on these skin color characteristics.

Development and validation of a new Skin Color Chart

Background: Age‐induced skin color variations are of great importance and incite increasing demand for cosmetic products to improve the appearance. The evaluation by clinicians or estheticians of the efficacy of skin care products is particularly difficult and requires the help of color charts.

Photothermal measurement of in-vitro stratum corneum hydration in a controlled humidity environment

We report measurements of in-vitro stratum corneum hydration under controlled humidity conditions. The measurements used an opto-thermal transient emission radiometry (OTTER) instrument with 2.94 μm Er:YAG excitation and wavelength selective detection, to maximise the sensitivity for water.