2-Mercaptonicotinoyl glycine prevents UV-induced skin darkening and delayed tanning in healthy subjects: A randomized controlled clinical study.

BACKGROUND: Chronic nonextreme sun exposure induces two mechanisms of skin pigmentation, causing immediate darkening and delayed tanning. A new molecule, 2-mercaptonicotinoyl glycine (2-MNG), has been shown in vitro to inhibit both immediate darkening and new melanin synthesis via covalent conjugation of the thiol group of 2-MNG to melanin precursors. OBJECTIVE: To evaluate 2-MNG in preventing both mechanisms in vivo. METHODS: In a randomized, intra-individual and controlled study, 33 subjects with melanin-rich skin were exposed to UV daylight on designated areas on the back and treated with a cosmetic formula containing 0.5% or 1% 2-MNG alone or 0.5% 2-MNG in association with lipohydroxy acid (LHA, 0.3%) plus Mexoryl-SX (MSX, 1.5%). The respective vehicles were used as controls and 4-n-butyl-resorcinol (4-n-BR, 2.5%) as a positive reference. RESULTS: 2-MNG alone significantly reduced immediate darkening and inhibited new melanin production when compared with vehicle, with higher performance at 1% than at 0.5%. 2-MNG at 0.5% in association with LHA and MSX showed significantly higher performance than 2-MNG 0.5% alone. 2-MNG at 0.5% and 1% showed significantly better performance than 4-n-BR. CONCLUSIONS: 2-MNG inhibited both UV-induced skin pigmentation mechanisms in vivo. The association of 2-MNG with LHA plus MSX showed the highest efficacy on melanin-rich skin with pigmentation induced by UV exposure.

Concealing a shiny facial skin appearance by an Aerogel-based formula. In vitro and in vivo studies.

OBJECTIVE: To explore, in vitro and in vivo, the potential interest of an Aerogel-based formula, in concealing a naturally shiny facial skin. METHODS: In vitro, various formulae and ingredients were applied as a thin film onto contrast plates and studied through measuring the shine induced following pump spraying of a mixture of oleic acid and mineral water as a sebum/sweat mix model. In such a test, an Aerogel ingredient led to very positive results. In vivo, two different formulae with various concentrations of Aerogel were randomly tested on half side of the face vs. bare side of Chinese women, under some provocative environmental conditions, known to enhance facial shine. These conditions comprised a normal activity under a hot and highly humid summer time followed - or not - by a hamam session. Both studies included comparative evaluations using a half-face procedure (treated/untreated or vehicle). In the first case, evaluations were quantitatively carried out, whereas the second one was based on a quantitative self-evaluations from standardized full-face photographs RESULTS: In vitro, the tested Aerogel, incorporated at 1% or 2% concentration in a common O/W cosmetic emulsion, shows an immediate light scattering effect, thereby masking shine. Such effect appears of much higher amplitude than that of two other tested particulate ingredients (Talc and Perlite). A noticeable remanence of anti-shine effect was confirmed in vivo in extreme conditions. The latter was self-perceived by all participants in the second study. This result is likely related to the super hydrophobic behaviour of the Aerogel. CONCLUSION: As cosmetic ingredient, this new Aerogel appears as a highly promising ingredient for concealing the facial skin shine, a source of complaint from many consumers living in hot and humid regions.

Nonablative remodeling: clinical, histologic, ultrasound imaging, and profilometric evaluation of a 1540 nm Er:glass laser.

BACKGROUND: Nonablative remodeling has been recently proposed as an alternative to CO2 and Er:YAG resurfacing. OBJECTIVE: To evaluate the efficacy and safety of a 1540 nm Er:glass laser with contact cooling in nonablative skin remodeling, focused on perioral and periorbital rhytides. METHODS: Sixty patients (mean age 47 years), Fitzpatrick skin types I-IV were treated four times over 6-week intervals. Patients were evaluated using digital photographs, histology, ultrasound imaging, and profilometry with silicone imprints in order to quantitate the degree of clinical improvement. RESULTS: All subjects reported subjective improvement in the quality and visual aspect of their skin. This was confirmed by a 40.2% reduction of anisotropy (P <.001) 6 weeks after the fourth treatment. Ultrasound imaging demonstrated a 17% increase of dermis thickness (P <.005). Biopsy specimens showed evidence of new collagen formation. CONCLUSION: This study has clearly demonstrated that irradiation with 1540 nm Er:glass laser can lead to new collagen formation, dermis thickening, reduction of anisotropy of the skin, and clinical improvements. The lack of adverse effects confirmed that this 1540 nm laser emitting in a pulsed mode coupled with an efficient cooling system is safe.

Use of thigh pressure cuffs to modulate simulated microgravity-induced changes in the skin measured with high-resolution B-scan ultrasound.

OBJECTIVE: The aim of the present study was to evaluate the fluid shift in a simulated microgravity experiment and to test the use of thigh cuffs to help alleviate the problem. METHODS: The change in skin thickness was assessed by a 20 MHz B-scan ultrasound device. This was performed on eight volunteers who underwent two successive 7-day periods of -6 degrees anti-orthostatic bed-rest, with or without the daytime use of thigh cuffs. The thigh cuffs were used to counteract the development of facial oedema. RESULTS: In the control group (without thigh cuffs), the results showed a steady increase in skin thickness of the combined dermis and hypodermis of the forehead and a reduction of the thickness of this tissue on the tibia. For the countermeasure group, although thigh cuffs were only employed during the daytime - being removed at night - their use reduced the amplitude and kinetics of the fluid shift, resulting in greater beneficial effects at the end of the day than early in the morning. CONCLUSION: These results of objective measurements of skin made using a non-invasive high frequency ultrasonography method confirm reports by cosmonauts of a reduction in facial oedema and a more 'comfortable' adaptation to microgravity by the use of thigh cuffs during space flight. This system is potentially promising for investigating fluid shifts in the skin and may prove useful in the evaluation of some oedematous skin diseases, as well as their therapy.

Skin topography measurement by interference fringe projection: a technical validation.

BACKGROUND/AIMS: The quantitative analysis of skin topography is frequently used in cosmetology to evaluate the efficacy of hydrating or anti-wrinkle creams (micro-topography studies) or creams for slimming or to alleviate stretch marks (macro-topography studies). Numerous methods involving the three-dimensional (3-D) reconstruction of the topography from silicone replicas have been developed. Some of the main techniques applied include optical profilometry based on the reflection of oblique lighting or on transparency, and profilometry by laser focusing or triangulation. METHODS: We chose to test the Dermatop system developed by Eotech Co., which is based on interference fringe projection profilometry associated with the Toposurf surface processing software. Owing to the system's principle of operation, we first ran three experiments to evaluate the influence of ambient lighting on the 3-D reconstruction and the surface roughness parameters, the influence of the calibration device built into the acquisition system and the influence of calibration in terms of ambient lighting correction. We then evaluated the accuracy, the repeatability and the reproducibility of the measurements provided by the system from known metal topographic standards and skin replicas. RESULTS: It was seen that external lighting can cause variations in the calculation of parameters SPa, SPt and SPtm which can reach error levels of about 5% if the operator does not almost systematically calibrate the apparatus between each measurement. These three experiments enabled us to standardise the protocol for the acquisition of 3-D information, in order to minimise the lighting problems and yet respect the requirements for routine studies. The correlation coefficient between the theoretical values and the mean of experimental values was 0.9955 for parameter SPa and 0.9983 for parameter SPtm. Repeatability presented variations of under 4%, irrespective of the parameters, and reproducibility of under 6%. CONCLUSIONS: The technique provides very satisfactory results from the point of view of accuracy, repeatability and reproducibility. It is an excellent compromise between cost, accuracy and the time required.

Skin ageing: changes of physical properties of human skin in vivo.

We have investigated in vivo the change with age of various parameters that describe the physical properties of skin. The parameters were derived from pressure/displacement curves obtained by applying reduced pressure to a small area of skin and measuring the resulting displacement by 20 MHz scan echography. By fitting the pressure/displacement curves to a theoretical model, the following skin parameters were obtained: E, Young's modulus or stiffness (in Pascals); sigma(0), the initial stress (in Pascals); and the unrestored energy ratio (UER), an index related to cutaneous non-elasticity. These parameters, which are used in mechanics to define the intrinsic physical characteristics of materials, were measured for the first time on volar forearm skin of 206 male and female subjects, aged between 6 months and 90 years. The results showed that skin thickness increases until maturity and decreases for women over 50-60 years old, Young's modulus E increases linearly with age, and ageing is divided into two phases for natural stress, sigma(0) and the non-elasticity index UER. Natural stress sigma(0) increases until maturity and then rapidly decreases. The non-elasticity index decreases until puberty and steadily increases after puberty. This new procedure provides a simple quantitative assessment of the physical properties of the skin, revealing that the skin becomes thinner, stiffer, less tense and elastic with ageing.

Estimation of the correlation amplitude of RF signals in small cutaneous vessels.

Time domain correlation technique is a widely used method for blood flow velocity measurement. The time shift between a pair of windowed ultrasonic echoes is estimated by searching the temporal position of the maximum of the interpolated normalized correlation function. Between two consecutive echoes, the acoustical footprint of a group of scatterers, which are transported with the flow, moves and is deformed. This implies a decreasing of the amplitude of the normalized correlation coefficient. In the case of microcirculation (low flow rate, low SNR), the amplitude of the correlation peak can be used to detect the presence of blood flow and to discriminate false and true detections (reliability index). We have numerically evaluated the statistical performances of the cross-correlation algorithm used as a correlation peak amplitude estimator in severe conditions (short correlation window length, low SNR). These theoretical results have been compared with in vitro experimentation on a 100-/spl mu/m-diameter microcirculatory phantom and with in vivo experimentation on a 180-/spl mu/m-diameter vessel of a human leg carrying erysipelas.

Characterisation of gravity-induced facial skin oedema using biophysical measurement techniques.

BACKGROUND/AIMS: In humans, the microgravity environment can be expected to induce swelling of facial tissues and shrinking of the tissues in the lower limbs, together with a loss in body weight. To evaluate fluid shifts in skin, the head-down bed-rest model was used. The aim of the present study was to evaluate the appearance of facial oedema in subjects undergoing anti-orthostatic bed-rest at an angle of -10 degrees. METHODS: The forehead of each of four subjects was measured before and after 1, 10 and 24 h in this head-down tilt position. At these time points, interstitial fluid migration and facial oedema were assessed using a high resolution B-scan ultrasound and a device for measuring the skin's mechanical properties. RESULTS: The results obtained showed a progressive increase in dermal thickness and initial stress, and a reduction in stiffness and elasticity of the skin during the study period. CONCLUSIONS: This preliminary study has demonstrated the feasibility of the method in measuring fluid displacement and retention in the skin. Furthermore, it highlights the influence of fluids on the mechanical behaviour of the skin. These techniques could be used for studying the redistribution of liquid masses during periods spent in space.

In vivo model of the mechanical properties of the human skin under suction.

BACKGROUND/AIMS: A new method for the in vivo characterization of the mechanical properties of skin has been developed. This comprises a suction chamber and an ultrasound device to measure both the vertical displacement of the skin's surface, and the skin's thickness. METHODS: A mathematical model of the mechanical behaviour of a taught elastic membrane is used to obtain a set of parameters intrinsic to the skin, such as Young's modulus (E) and the initial stress (sigma0), which reflect the stiffness and the natural tension of the skin, respectively. We also calculated an index of non-elasticity of the skin (unrestored energy ratio, UER), which takes into account the volume of tissue mobilized. It determines a ratio between the energy input to the skin and the energy it dissipates. These parameters were evaluated from the volar forearm of 10 normal male volunteers. RESULTS: The results were: 129+/-88 kPa for E, 13.5+/-5 kPa for sigma0, and 0.42+/-0.04 for UER; with reproducibilities of 9.5%, 12.4% and 6.4%, respectively. CONCLUSIONS: This new suction device was found useful for the study of the behaviour of the skin, and the device may be used for the evaluation of certain skin diseases and their therapy.

Evaluation of cutaneous modifications in seventy-seven growth hormone-deficient children.

Cutaneous parameters such as dermal thickness, stiffness, elasticity, skin surface lipid and hydration were evaluated using noninvasive methods in 77 growth hormone-deficient (GHD) children before replacement therapy and in 70 non-GHD children. We showed that in GHD children, dermis was thinner (0.70 +/- 0.10 vs. 0.80 +/- 0.10 mm, p < 0.0001 for prepubertal children and 0.81 +/- 0.10 vs. 0.94 +/- 0.11 mm, p < 0.0001 for pubertal children), stiffer (178.5 +/- 57.3 vs. 113.09 +/- 37 kPa, p < 0.0001 for prepubertal children and 172.5 +/- 61.7 vs. 117.3 +/- 42.5 kPa for pubertal children, p < 0.001) and less elastic (0.44 +/- 0.09 vs. 0.39 +/- 0.06 (nonelasticity index), p < 0.01 for prepubertal children and 0.39 +/- 0.05 vs. 0.33 +/- 0.04, p < 0.001 for pubertal children) compared to controls. Fourteen GHD children were re-evaluated after 1 year of GH treatment: dermal thickness and skin stiffness were significantly improved (p < 0.001 and p < 0.05 respectively) while elasticity was not modified. During the same period, 11 controls did not show any significant cutaneous modification. IGF-1 values, but not IGFBP-3 values, correlated positively with dermal thickness in GHD children, before and after 1 year of GH treatment. To conclude, GHD children exhibited specific cutaneous modifications. In a subset of GHD children, we showed that these modifications were influenced by GH treatment. More extensive studies are needed to see if these changes correlated with other GH effects.

Sex- and site-dependent variations in the thickness and mechanical properties of human skin in vivo.

A new method for the in vivo characterization of the physical properties of skin is presented. This comprises an ultrasound device to measure the vertical displacement of the surface of the skin, as well as its thickness and that of the hypodermis under suction. In combination with this, a mathematical model is used to calculate the following skin parameters: Young's modulus, the initial stress and an index of non-elasticity. These parameters were evaluated from the volar forearm and the forehead of 30 male and 30 females, of similar ages (28 +/- 6-years-old). The sensitivity of the testing procedure, allowing the characterization of the mechanical parameters of the skin, easily differentiated these two sites, and in some cases, differences between women and men were demonstrated. The main results showed for both sexes that the thickness (P = 0.0001), Young's modulus (P = 0.0001), and the index of non-elasticity (P = 0.0001) were greater for the forehead than for the ventral forearm, but that the initial stress was lower (P = 0.0001). The results show that the skin is thicker, stiffer and less tense and elastic on the forehead than on the ventral forearm, suggesting structural differences between these two sites (collagen fibre network, elastic fibres, epidermis, stratum corneum, microvascularization, actinic damage, presence of sebaceous glands, etc.). It is hoped that this device will be useful for the evaluation of certain skin disorders (scleroderma, Ehlers-Danlos syndrome, cutis laxa, oedema, etc.) and their therapy, as well as being a useful tool in skin ageing and cosmetic product assessment.

Efficacy of topical 0.05% retinaldehyde in skin aging by ultrasound and rheological techniques.

BACKGROUND: The natural precursor of retinoic acid, i.e. retinaldehyde, has been proven to exert retinoid activities. AIM AND METHODS: The aim of this prospective instrument study was to determine the effect of topical retinaldehyde 0.05% on the physical properties of aging skin. This was performed using two devices, namely a high-resolution (70-80 microm) ultrasound scanner, which visualizes the thickness of both the epidermis and the dermis, and an echorheometer, which assesses the stiffness and elasticity of the skin by suction. In a 1-year study, 21 patients applied retinaldehyde cream 0.05% on the face, while another group of 19 volunteers were only treated with an emollient (control group). Epidermal and dermal thicknesses were measured on the forehead and temple, and stiffness and elasticity were measured on the forehead only. All the instrumental parameters were assessed at baseline and at the end of treatment. RESULTS: Compared to the control group, retinaldehyde treatment induced a significant increase in epidermal thickness of the temple, as well as in cutaneous elasticity (p < 0. 01). Similarly, retinaldehyde treatment tended to increase dermal thickness and reduce cutaneous stiffness, but no statistical difference could be observed between the two groups. CONCLUSION: Taken together, the results further suggest that retinaldehyde has counteracting effects on skin aging

An in vivo method for measuring the mechanical properties of the skin using ultrasound.

In this study, we report a new and original device called the "echorheometer," comprising a suction system with an ultrasound scanner (A-mode, TM-mode and B-mode) that enables the simultaneous visualization and measurement of the deformation of skin structures in vivo. With the scanner described here, high resolution is obtained using a strongly focused, wide-band 20-MHz center frequency transducer, with an axial resolution of 0.07 mm. This device can determine, noninvasively, not only those skin structures that are involved in the deformation, but also their morphological variation and their extent of involvement with the degree of stress applied. Using this device, the behavior of the dermis and subcutaneous fat, while under suction, was investigated on the volar forearm of 10 volunteers. The results showed that the resistance to the applied vertical stress is essentially due to the dermis rather than the subcutaneous fat, and that there is a certain amount of infiltration of fluid into the tissues under suction. In addition, it was shown that the dermal response to an applied suction is initially due to its own natural tension and that, with increasing deformation, the intrinsic dermal elasticity has a greater contribution to the resistance of stress. With this information, we hope to develop a mechanical model to define appropriate mechanical parameters for skin. This will allow the evaluation of changes in the dermis and also enable therapeutic intervention to be assessed. Furthermore, it could also be applied to studies of skin ageing and the assessment of cosmetic product efficacy (emolliency, hydratation, etc.).

Study of cutaneous extensibility in lymphoedema of the lower limbs.

We have studied changes in the elasticity and viscosity of the skin in patients with lymphoedema, using a technique involving vertical extensibility by suction. We measured parameters which included immediate extensibility (Ue, which reflects the elastic properties of the skin), and delayed extensibility (Uv which reflects intracutaneous movements of a viscous type). In grade III lymphoedema, Ue is decreased and Uv is increased. These changes are explained by volume variations and histological alterations, and tend to normalize after treatment. Our study shows that measurement of extensibility is useful in evaluation of volume variations, effects of therapy, and disease evolution, as Ue variations correlate with volume variations and with Uv changes. This technique also provides information which is useful in assessing patients' functional difficulties in relation to skin infiltration, and might be of value in lymphoedema follow-up.

Effects of short-time hydration on skin extensibility.

Vertical cutaneous extensibility was studied before and after 1, 2, 5 and 10 min hydration by application of tap water. After hydration, we noted an increase in all rheological parameters linked to elasticity whereas viscosity and hysteresis parameters were unmodified. These modifications took place from the first minute and increased thereafter. Men and women showed identical values prior to hydration. After hydration, an extensibility gain was noted only in the women, men's extensibility being unmodified. Studying rheological behaviour as a function of age, we showed similar modifications in younger and older groups, the extensibility gain being greater in the older group. Prior to hydration, the stratum corneum was extremely rigid and extensibility was comparable between men and women. Hydration, softening the horny layer, allows a rapid extensibility gain proportional to the reduced thickness of the dermis, especially in women and older subjects.