Quantitative assessment of skin aging.

Noninvasive methods have allowed physicians to give an objective description of aged skin in terms of functional and esthetic properties. The relative influence of environment (mainly sun) on the true aging process can be assessed through the obtained data. It is also possible to measure the efficacy of topical preparations (cosmetics or drugs) designed for treating the various cutaneous aging marks.

EEMCO guidance for the assessment of skin topography. The European Expert Group on Efficacy Measurement of Cosmetics and other Topical Products.

Numerous factors can modify the visibility or the actual dimensions of the skin microrelief and wrinkles. To quantify these changes, several methods, including clinical and non-invasive ones, have been proposed. This article reviews the advantages et drawbacks of all of them and lists some experimental recommendations to make the results of studies using these methods, more reliable.

Echographic assessment of corticosteroid-induced skin-thinning, including echogenicity measurement.

BACKGROUND/AIMS: Skin atrophy is one of the main side effects of long-term topical corticosteroid therapy. It has already been studied through ultrasound skin-thickness measurement. In this study, the quantification of dermal echogenicity was introduced to provide new information on this phenomenon. METHODS: Skin thinning induced by topical application (without occlusion) of the superpotent corticosteroid clobetasol propionate (0.05% lotion), was assessed by means of ultrasonography in terms of thickness and echogenicity. 15 healthy volunteers were treated for 6 weeks, 1 daily, 5 days a week on the forearms. RESULTS: The thinning showed a biphasic pattern, with a 1st period of rapid change (about 15% of thinning in a week) followed by a period of slower but significant change. Skin thickness returned to baseline values 3 weeks after the end of treatment. Dermal echogenicity, which represents the mean intensity of the ultrasound signals reflected by the dermis, was found to follow the same variations, increasing strongly during the 1st week, then more slowly. The 2 parameters are correlated and probably reflect the same physiological modifications responsible for skin thinning, i.e., a reduction in glycosaminoglycan synthesis (leading to a drastic fall in dermal water content) and vasoconstriction. CONCLUSION: This sensitive and non invasive method enables us to identify the effects of clobetasol propionate on the healthy dermis in the absence of any clinical signs of thinning.

Assessment of aging of the human skin by in vivo ultrasonic imaging.

The ultrasonic imaging technique that we have developed provides cross-sectional images of human skin in vivo with a resolution of about 80 microns axially (i.e., deep into the skin) and 250 microns lateral (parallel to the surface). In order to study aging skin, we obtained ultrasonic images from the mid-forearm (volar and dorsal sides) of 142 women. Ultrasonically, on the images, the dermis appears composed of two bands: a dark superficial one where the ultrasonic waves are propagated in a relatively homogeneous or non-echogenic medium, and a deeper one, which is lighter in color, suggesting a heterogeneous medium. Our results show that skin is thicker on the dorsal than on the volar forearm. In contrast to previously published results, skin thickness remains constant until the seventh decade of life, diminishing thereafter. The relative thickness of the two bands show marked variations with age: a progressive thickening of the dark band, from zero in infants to approximately 75% of total skin thickness in aged subjects, while the light band shows the inverse trend. Comparing the amplitude of the bands on the volar and dorsal forearm, the relative thickness of the dark band is larger on the dorsal (exposed) side and increases with age. These findings and the analysis of variously stained biopsies taken in some of our patients lead us to assign this dark band to a zone in the upper dermis where the collagen network is delicate, dense, and well organized. This is supported by some data in the literature. The thickness of this subepidermal non-echo-genic band appears to be a far more sensitive marker of skin aging at the dermal level than is the measurement of skin thickness.

Assessment of topical non-steroidal anti-inflammatory drugs.

A new non-invasive technique for assessing the efficacy of topical non-steroidal anti-inflammatory drugs (NSAID) in man is proposed. The NSAID are initially applied to the skin under occlusion before inflammation is induced by a methyl nicotinate solution. The inflammatory response is quantified in terms of cutaneous blood flow by a laser Doppler velocimeter (LDV). The efficacy of NSAID preparations is calculated by comparing the responses of the LDV to the methyl nicotinate challenge on the pretreated and the non-treated skin sites. This protocol has been used to investigate the effect of three different NSAID preparations (indomethacin, niflumic acid, palmitoyl collagenic acid) and the influence of the vehicle on the efficacy of indomethacin. The three preparations tested gave positive results but with different amplitudes in response. The efficacy of indomethacin varied with the vehicle used.

An in vivo assessment of the biomechanical properties of human skin modifications under the influence of cosmetic products.

Synopsis A new device using a torsional technique has been developed to record the biomechanical properties of the skin. After determination of the optimal experimental conditions, effects of cosmetic products on the stratum corneum biomechanical properties are described.