Roland Bazin

A computational skin model: fold and wrinkle formation

This paper presents a computational model for studying the mechanical properties of skin with aging. In particular, attention is given to the folding capacity of skin, which may be manifested as wrinkles. The simulation provides visual results demonstrating the form and density of folds under the various conditions. This can help in the consideration of proper measures for a cosmetic product for the skin.

Influence of age on the wrinkling capacities of skin

Background: Comparisons of clinical assessment with measurement of physical parameters are rare.

Oral contraceptives alter circadian rhythm parameters of cortisol, melatonin, blood pressure, heart rate, skin blood flow, transepidermal water loss, and skin amino acids of healthy young women.

Sixteen healthy women users and nonusers of oral contraceptives (OC) volunteered to document a set of circadian rhythms. Nine were taking OC providing ethynyl estradiol (0.03-0.05 mg/24h, 21 days/month) combined with DL- or L-norgestrel or norethisterone. There was no group difference (p > 0.05) in median age (22 years), weight (57 kg), and height (162) cm). Data were obtained at fixed hours, 5 times/24h, during a 48-h span, in November. (Day activity from approximately 08:00 to approximately 23:00 h and night rest). Environmental conditions were controlled, using air-conditioned rooms of constant temperature (26 degrees +/- 0.5) and relative humidity 45% +/- 1. Both cosinor and ANOVA were used for statistical analyses. All circadian rhythms were validated with one exception: that of salivary melatonin was not detected in OC users. The 24h mean (M) exhibited group differences for certain variables: M was greater in OC than non-OC users for systolic blood pressure (p < 0.0001), heart rate (p < 0.01), skin blood flow (p < 0.04), and transepidermal water loss (p < 0.02). M was lower in OC than non-OC users in salivary cortisol (p < 0.04) and skin amino acids (p < 0.003). No group difference was detected in any other documented rhythms: diastolic blood pressure, grip strength of both hands, oral temperature, self-rated fatigue, and the skin variables of urea, lactate, triglycerides, and acid phosphatase activity.

Effect of the sun on visible clinical signs of aging in Caucasian skin

Objectives Aging signs can be classified into four main categories: wrinkles/texture, lack of firmness of cutaneous tissues (ptosis), vascular disorders, and pigmentation heterogeneities. During a lifetime, skin will change in appearance and structure not only because of chronological and intrinsic processes but also due to several external factors such as gravity, sun and ultraviolet exposure, and high levels of pollution; or lifestyle factors that have important and obvious effects on skin aging, such as diet, tobacco, illness, or stress. The effect of these external factors leads to progressive degradations of tegument that appear with different kinetics. The aim of this study was to clinically quantify the effect of sun exposure on facial aging in terms of the appearance of new specific signs or in terms of increasing the classical signs of aging. Materials and methods This study was carried out on 298 Caucasian women from 30 years to 78 years old. The participants were divided into two groups according to their sun exposure history: 157 women were characterized as sun-seeking, and the other 141 were classified as sun-phobic. This division was made possible by dermatologist grading of heliodermal status on the basis of several observations of classic criteria: wrinkles, sagging, pigmentation heterogeneities, vascular disorders, elastosis, and so on. This work was an opportunity to complete clinical photographic tools by adding in our portfolio new scales for signs observed in the two groups. Thus, 22 clinical parameters were investigated by a panel of twelve trained experts to characterize each woman’s face regarding standardized photographic scales, and thus describe the aging process. Results By calculating statistical correlations between the four clinical clusters (wrinkles/texture, ptosis, vascular disorders, and pigmentation disorders), and real age and apparent age on the one hand and heliodermal status on the other hand, we identified a link between each clinical cluster and aging and the photoaging process. By comparing evaluations of clinical signs between the two groups for each 10-year cluster, we demonstrated that whatever the age, a prevalence of pigmentation disorders for the sun-seeking group (ie, pigmentation) is strongly linked to ultraviolet (UV) exposure. Meanwhile, clinical signs of ptosis are linked more to chronological aging and do not present differences between the two groups, nor, therefore, photoaging. Wrinkles and texture are affected by the two aging processes. Finally, clinical signs of vascular disorders present no evolution with age. Conclusion Clinical signs of aging are essentially influenced by extrinsic factors, especially sun exposure. Indeed UV exposure seems to be responsible for 80% of visible facial aging signs.

Influence of season on some skin properties: winter vs. summer, as experienced by 354 Shanghaiese women of various ages

The facial skin of 354 women, aged 18–80, living in Shanghai, was investigated over two successive 6 month periods, summer and winter. Results from clinical assessments indicate that aging signs, such as wrinkling and sagging, are unaffected over such period.

Circadian dosing time dependency in the forearm skin penetration of methyl and hexyl nicotinate

The forearm skin penetration of hydrophilic methyl nicotinate (MN) and lipophilic hexyl nicotinate (HN) was assessed around the clock. The sixteen healthy women (median age: 22 years, weight: 57 kg and height: 162 cm) who volunteered for the study were synchronized with a diurnal activity from 07.00h (+/- 1h) to 23.00h (+/- 1h.30min) and a nocturnal rest before and during the 48h sojourn in air-conditioned rooms (26 degrees C +/- 0.5 degrees C). Both HN (0.5% ethanol solution) and MN (5% ethanol solution) have a vasodilative effect on dermal vessels. The lag time (LT) between the delivery of a fixed volume (10 microliters) of the agent at the skin surface and the beginning of the vasodilatation, detected with a laser-Doppler method, was used to quantify the penetration kinetics. Tests were performed every 4h, at fixed clock hours, over a span of a 40h. Two types of tests were done with each of the agents: fixed site (one site only) and shifted sites (10 different places). Both cosinor and ANOVA have been used for statistical analyses. The shortest LT (fastest penetration) was located around 04.00h. The longest LT (slowest penetration) occurred during the day with a single peak around 13.00h in three of the situations, or two peaks (HN with fixed site). A rather large rhythm amplitude (peak-to-trough difference larger than 50% of the 24h mean LT) was validated.

Clinical study on the effects of a cosmetic product on dermal extracellular matrix components using a high-resolution multiphoton tomograph.

Background/purpose: The aim of this study was to demonstrate the effects of selected plant extracts in a cosmetic cream on the dermal network components after a 3‐month treatment using an in vivo multiphoton tomographic device.

Facial skin pores: a multiethnic study

Skin pores (SP), as they are called by laymen, are common and benign features mostly located on the face (nose, cheeks, etc) that generate many aesthetic concerns or complaints. Despite the prevalence of skin pores, related literature is scarce. With the aim of describing the prevalence of skin pores and anatomic features among ethnic groups, a dermatoscopic instrument, using polarized lighting, coupled to a digital camera recorded the major features of skin pores (size, density, coverage) on the cheeks of 2,585 women in different countries and continents. A detection threshold of 250 μm, correlated to clinical scorings by experts, was input into a specific software to further allow for automatic counting of the SP density (N/cm2) and determination of their respective sizes in mm2. Integrating both criteria also led to establishing the relative part of the skin surface (as a percentage) that is actually covered by SP on cheeks. The results showed that the values of respective sizes, densities, and skin coverage: 1) were recorded in all studied subjects; 2) varied greatly with ethnicity; 3) plateaued with age in most cases; and 4) globally refected self-assessment by subjects, in particular those who self-declare having “enlarged pores” like Brazilian women. Inversely, Chinese women were clearly distinct from other ethnicities in having very low density and sizes. Analyzing the present results suggests that facial skin pore’s morphology as perceived by human eye less result from functional criteria of associated appendages such as sebaceous glands. To what extent skin pores may be viewed as additional criteria of a photo-altered skin is an issue to be further addressed.

Longitudinal study of skin aging: from microrelief to wrinkles

Aim: To study the changes in skin microrelief and periocular wrinkles during the aging process.

Photoaging of the chest analyzed by capacitance imaging

Objective: Capacitance imaging is a new technique using sensors based on silicon technology developed to record fingerprints for security reasons. Applying such a sensor onto the skin surface gives the capacitance (hydration) map of the skin surface with a two‐dimensional resolution of 50 μm. This method was used to characterize skin of the chests of 64 women with various grades of skin photoaging.