Infant skin maturation: Preliminary outcomes for color and biomechanical properties.

BACKGROUND: Newborn infant skin changes after birth but studies have focused on the epidermal barrier. Dermal properties are relevant for care, but literature on postnatal changes is sparse. We further characterized skin maturational changes in lightness, color and response to biomechanical stress. METHODS: Normal skin sites from subsets of participants in a trial on the progression and stage of infantile hemangiomas were retrospectively examined. Standardized photographs were analyzed as L*, a*, and b* images. Biomechanics were measured with the Cutometer® . RESULTS: Color changed significantly with increasing age. Skin was darker and redder at 2.0 vs. 5.4, 8.5 and 12.8 months. Yellow color increased, with higher values at 12.8 vs. 2.0, 3.5 and 5.4 months. Chest tissue was consistently more elastic than arm and face sites, with significantly higher elasticity for the youngest and oldest age groups. Biological elasticity, elastic recovery, and total recovery were significantly greater for the oldest subjects. Viscoelasticity and elastic deformation were lower at 5.5 vs. 8.8 and 17.6 months. Arm viscoelastic creep was highest at 2.8 months. CONCLUSION: Skin maturation continues into year two. Increasing elasticity and decreasing viscoelasticity may reflect increased collagen structure/function. The findings have implications for prevention of skin injury associated with mechanical forces.

Biomechanical properties of infantile hemangiomas: clinical stage and effect of age.

BACKGROUND: Infantile hemangiomas (IHs) are benign vascular neoplasms with rapid capillary proliferation shortly after birth and slow involution with diminishing capillary proliferative activity, fibrosis, and fatty replacement over 7-10 years. METHODS: Hemangiomas and contralateral control sites in 88 subjects were measured using a suction device, 6-mm probe and 200 mbar negative pressure. Mechanical properties were assessed vs. controls and effects of body site, depth, clinical stage, histology diagnosis, and time. RESULTS: Biological elasticity, overall elasticity, net elasticity, total recovery, and elastic recovery were lower for IH vs. controls (P < 0.001). IH total deformation, elastic deformation, viscoelastic creep, and residual deformation were higher than controls (P < 0.001). Involuting IHs had lower viscoelasticity than proliferating and stable lesions (P < 0.001) and lower viscoelastic creep than stable IHs (P = 0.04). IH viscoelasticity was higher at 2.3 than 12.9, 23.7, and 61.0 months and at 4.9 and 8.1 than 61.0 months. IH elastic recovery varied by body site with larger differences vs. control for abdomen and leg. Elastic recovery differences from control were smaller at younger vs. older ages. CONCLUSIONS: Measurement of biomechanical properties may be useful to characterize IH progression and treatment response in clinical settings.

The structural implications of water hardness metal uptake by human hair.

Human hair can extract significant levels of calcium and magnesium, water hardness metals, from tap water immediately following chemical treatments and during hygiene practices. We have previously shown that this uptake is primarily a function of the condition of the hair. Depending on the extent of chemical damage, the hair can extract notable amounts of water hardness metals even from soft water. As water hardness metals concentrate primarily in the cuticle layers of the hair fibre, it is hypothesized that their presence will affect the structural properties that are chiefly driven by the cuticle. We examined hair mechanics and styling by technical measures of single-fibre torsional and tensile properties, combability and style retention as a function of the calcium and magnesium content of virgin and bleached hair. Our work has indicated that water hardness can affect hair properties. Fibre stiffening was induced by the presence of water hardness metals inside the fibres of both virgin and bleached hair. A reduction in combing forces was also observed, and this effect is believed to be a result of the stiffening. The style retention of virgin hair was improved by water hardness metals, whereas that of bleached hair was slightly reduced.

Role of TNF-α polymorphism -308 in neurosensory irritation.

Neurosensory cutaneous discomfort in response to topical products is common, yet the relationship between symptoms such as stinging and visible irritation is currently unclear. The presence of a polymorphism at position -308 on the TNF-α gene has been associated with skin irritation, i.e., erythema, dryness. Individuals with a G to A transition (AA/GA genotypes) have a lower threshold to experimentally induced irritation than those with the wild type (G allele, GG genotype). We investigated the effect of this polymorphism on neurosensory irritation (NSI). DNA genotyping was used to determine the allele type amongst a population of health care workers. The neurosensory response to lactic acid and water on the nasolabial folds and hands was assessed using a quantitative lactic acid sting test. Both genotypes had a more intense response to lactic acid compared with water on the face. The AA/GA genotypes had directionally higher scores from lactic acid (P = 0.1) and significantly higher stinging intensities from water (P = 0.001) on the face. For the hands, stinging intensities were higher for lactic acid and water amongst the AA/GA genotypes (P = 0.03 and 0.006 respectively). NSI to lactic acid was significantly higher on the face than on the hands (P < 0.05). Our findings indicate that subjects with the A transition at position -308 on the TNF-α gene experience more intense NSI with common ingredients, i.e., lactic acid and water, than those with the wild type. TNF-α polymorphism -308 may account for some of the inter-individual variability in response to skin care practices.

The uptake of water hardness metals by human hair.

The objective of this work was to examine the variables that influence the interaction between water hardness metals and human hair. Hair extracts various constituents from the tap water used during daily hygiene practices and chemical treatments. Calcium and magnesium metal ions are the most prevalent and give water "hardness." Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was employed to quantify the metal content of hair, which was studied as a function of the following variables: hair condition (oxidative damage), level of water hardness, and water pH. We have demonstrated that these variables impact water hardness metal uptake to varying extents, and the effects are driven primarily by the binding capacity (available anionic sites) of the hair. The condition of the hair, a key representation of the binding capacity, was most influential. Interestingly, water hardness levels had only a small effect on uptake; hair became saturated with notable amounts of water hardness metals even after repeated exposure to soft water. Water pH influenced metal uptake since side chains of hair proteins deprotonate with increasing alkalinity. These insights highlight the importance to the hair care industry of understanding the interaction between water hardness metals and hair.

Mechanism of tyrosinase inhibition by deoxyArbutin and its second-generation derivatives.

BACKGROUND: Disorders, such as age spots, melasma and hyperpigmentation at sites of actinic damage, emanate from the augmentation of an increased amount of epidermal melanin. OBJECTIVES: The ineptness of current therapies in treating these conditions, as well as high cytotoxicity, mutagenicity, poor skin penetration and low stability of skin-depigmenting formulations led us to investigate new compounds that meet the medical requirements for depigmentation agents. We have shown previously that the tyrosinase inhibitor deoxyArbutin (dA) is a more effective and less toxic skin lightener than hydroquinone (HQ). METHODS: The efficacy and reversibility of dA and its derivatives on inhibiting tyrosine hydroxylase and DOPAoxidase was assessed using standard assays. RESULTS: dA and its second-generation derivatives inhibit tyrosine hydroxylase and DOPAoxidase activities of tyrosinase dose dependently thereby inhibiting melanin synthesis in intact melanocytes, when used at concentrations that retain 95% cell viability in culture. This depigmenting effect was completely reversible when the compounds were removed. Tyrosinase inhibition was also observed in vitro when tested using human and purified mushroom tyrosinase, establishing that they are direct enzyme inhibitors. Lineweaver-Burk reciprocal plot analysis using mushroom tyrosinase illustrated that dA and its derivatives are more robust competitive inhibitors than HQ, when tyrosine is used as substrate. CONCLUSIONS: Thus, dA and its second-generation derivatives, which inhibit melanogenesis at safe concentrations by specifically acting on the tyrosinase enzyme at a post-translational level, are promising agents to ameliorate hyperpigmented lesions or lighten skin.

Effect of oral intake of choline-stabilized orthosilicic acid on hair tensile strength and morphology in women with fine hair.

The appearance of hair plays an important role in people's overall physical appearance and self-perception. Silicon (Si) has been suggested to have a role in the formation of connective tissue and is present at 1-10 ppm in hair. Choline-stabilized orthosilicic acid ("ch-OSA") is a bioavailable form of silicon which was found to improve skin microrelief and skin mechanical properties in women with photoaged skin. The effect of ch-OSA on hair was investigated in a randomized, double blind, placebo-controlled study. Forty-eight women with fine hair were given 10 mg Si/day in the form of ch-OSA beadlets (n = 24) or a placebo (n = 24), orally for 9 months. Hair morphology and tensile properties were evaluated before and after treatment. Urinary silicon concentration increased significantly in the ch-OSA supplemented group but not in the placebo group. The elastic gradient decreased in both groups but the change was significantly smaller in the ch-OSA group (-4.52%) compared to placebo group (-11.9%). Break load changed significantly in the placebo group (-10.8%) but not in the ch-OSA supplemented group (-2.20%). Break stress and elastic modulus decreased in both groups but the change was smaller in the ch-OSA group. The cross sectional area increased significantly after 9 months compared to baseline in ch-OSA supplemented subjects but not in the placebo group. The change in urinary silicon excretion was significantly correlated with the change in cross sectional area. Oral intake of ch-OSA had a positive effect on tensile strength including elasticity and break load and resulted in thicker hair.

Assessment of skin absorption and irritation potential of arachidonic acid and glyceryl arachidonate using in vitro diffusion cell techniques.

Arachidonic acid (AA), a precursor of pro-inflammatory mediators, and its glycerin ester, glyceryl arachidonate (GA), are reportedly used in cosmetic products. In vitro skin penetration of AA and GA and GA's ester hydrolysis was determined in flow-through diffusion cells. AA penetration with human and rat skin was 19.5% and 52.3% of the applied dose respectively, a substantial amount of which remained in the skin at 24h. Similar penetration results were obtained with GA in human skin. However, GA penetration through cultured skin (EpiDerm) was 51% of the applied dose, almost all of which appeared in the receptor fluid. At least 27.8% of GA penetrating skin was hydrolyzed to AA. In vitro methods were used to assess skin irritation in diffusion cells. Skin irritation of AA, sodium lauryl sulfate (SLS), and Tween 80 was determined by changes in transepidermal water loss (TEWL), skin viability (3-(4,5-dimethylthiaxol-2-yl)-2,5-diphenyltetrazolium bromide, MTT, formation), and cytokine release (IL-1alpha). SLS irritation was much less pronounced in an emulsion versus an aqueous vehicle. No significant irritation was observed in vitro from AA in an emulsion. This work predicts that AA would penetrate human skin in vivo and that it could be formed in skin from topically applied GA.

Ontogeny of water sorption-desorption in the perinatal rat.

In mammals, birth marks a transition to a cold and gaseous environment that requires rapid physiologic adaptations limiting heat and water loss. In this study, the perinatal Sprague-Dawley rat was utilized as a model to study the behavior of water binding to the external body surface following birth. Water sorption and desorption were quantified by measurement of skin surface capacitance following water loading using a dry ring electrode system. The results indicate that the external body surface of the newborn rat is highly hydrophobic. This hydrophobicity is manifested by the rapid desorption of water (amniotic fluid) following birth as well as marked limitation of water sorption after birth. Post-natally, this hydrophobic effect is gradually lost over the first 3 d of life. Somatic growth retardation results in retention of this surface property, whereas extraction of the skin surface with acetone abolishes it. Morphologic and functional (water binding) studies performed after stripping the stratum corneum with acrylic adhesive strongly suggest a physiologic role for the periderm in determining this postnatal hydrophobic effect. These data are interpreted as evidence for a novel thermoregulatory mechanism in the rat during adaptation to post-natal life.

Keratinocytes play a role in regulating distribution patterns of recipient melanosomes in vitro.

Melanosomes in keratinocytes of Black skin are larger and distributed individually whereas those within keratinocytes of Caucasian skin are smaller and distributed in clusters. This disparity contributes to differences in skin pigmentation and photoprotection, but the control of these innate distribution patterns is poorly understood. To investigate this process, cocultures were established using melanocytes and keratinocytes derived from different racial backgrounds and were examined by electron microscopy. Melanosomes transferred to keratinocytes were categorized as individual or in various clusters. Melanosome size was also determined for individual and clustered melanosomes. Results indicate that, in our model system, melanosomes in keratinocytes from different racial backgrounds show a combination of clustered and individual melanosomes. When keratinocytes from dark skin were cocultured with melanocytes from (i) dark skin or (ii) light skin, however, recipient melanosomes were individual versus clustered in (i) 77% vs 23% and (ii) 64% vs 36%, respectively. In contrast, when keratinocytes from light skin were cocultured with melanocytes from (iii) dark skin or (iv) light skin, recipient melanosomes were individual versus clustered in (iii) 34% vs 66% and (iv) 39% vs 61%, respectively. These results indicate that recipient melanosomes, regardless of origin, are predominantly distributed individually by keratinocytes from dark skin, and in membrane-bound clusters by those from light skin. There were also differences in melanosome size from dark or light donor melanocytes. Melanosome size was not related to whether the melanosomes were distributed individually or clustered, however, in cocultures. These results suggest that regulatory factor(s) within the keratinocyte determine recipient melanosome distribution patterns.

Surface electrical capacitance as a noninvasive index of epidermal barrier in cultured skin substitutes in athymic mice.

Restoration of an epidermal barrier is a definitive requirement for wound closure. To determine formation of an epidermal barrier as a function of hydration of the stratum corneum, we measured surface electrical capacitance (SEC) of the epidermis in cultured skin substitutes (CSS) in vitro and after grafting to athymic mice. CSS were prepared from human keratinocytes and fibroblasts attached to collagen-glycosaminoglycan substrates. On culture days 3, 7, 14, 17, and 21, SEC was measured in situ. CSS (n = 18; mean +/- SEM) showed a time-dependent decrease of SEC (picoFarads, "pF") from 4721 +/- 28 pF on day 3 to 394 +/- 117 pF on day 14, and subsequent increase to 1677 +/- 325 pF on day 21. After 14-d incubation, parallel CSS samples (n = 5) or murine autografts (n = 5) were grafted orthotopically to athymic mice. After grafting, CSS showed decreases in SEC from 910 +/- 315 pF at 2 wk to 40 +/- 10 pF at 4 wk with no significant decreases thereafter. Control values for murine autograft were 870 +/- 245 pF at 2 wk, and 87 +/- 30 pF at 4 wk. SEC values for native murine skin (n = 10) were 91 +/- 18 pF, and for native human skin (n = 10) were 32 +/- 5 pF. The data demonstrate that SEC decreases with time in culture and that healed or intact skin has approximately 10- to 100-fold lower SEC than CSS in vitro. This noninvasive technique provides a quantitative index of epidermal barrier in CSS in vitro and demonstrates the development of functional epidermal barrier during healing of wounds treated with cultured skin substitutes.

Surface electrical capacitance as a noninvasive bedside measure of epidermal barrier maturation in the newborn infant.

OBJECTIVE: The classical studies of epidermal barrier function in infants have relied on measurement of transepidermal water loss by evaporimetry. This technique, although valuable, is, in practice, slow, expensive, and susceptible to error because of convective air currents. In this prospective study, we evaluated gestation-dependent and postnatal age-dependent changes in epidermal barrier function by measurement of skin surface electrical capacitance (SEC) in 40 newborn infants ranging from 25 to 40 weeks' gestational age. SEC was measured in picofarads with a dermal phase meter. METHODOLOGY: The measurements were recorded continuously during a 12-second period from the forehead at 12 to 24 hours of life. The baseline (CBL) surface hydration at 1 second and the rate of change of SEC during probe occlusion (CSL) were used as measures of surface hydration and transepidermal water movement, respectively. In the most premature infants (< 30 weeks), these measurements were repeated daily for 5 days. Data were analyzed by analysis of variance after logarithmic (Ln) transformation. RESULTS: We found a significant difference in Ln(CBL) in infants born before and after 30 weeks' gestation (4.91 +/- 0.36 Ln[pF] vs 2.67 +/- 0.21 Ln[pF], respectively). Similarly, CSL was significantly different in infants born before and after 30 weeks' gestation (16.42 +/- 5.55 pF/s vs 1.59 + 0.22 pF/s, respectively). In infants born at less than 27 weeks, both Ln(CBL) and CSL decreased significantly by postnatal day 5. In the term group (n = 25), CSL was significantly greater in white than in black infants (1.96 +/- 1.32 pF/s vs. 0.95 +/- 0.55 pF/s, respectively). CONCLUSION: These results demonstrate impaired epidermal barrier properties in immature infants, less than 30 weeks' gestation, and reveal a remarkable rate of barrier maturation of this group in the first few days of postnatal life. Also, the finding of decreased CSL in black infants supports the hypothesis of differences in barrier function attributable to skin types. Overall, these findings demonstrate the feasibility of bedside SEC measurements in the evaluation of epidermal barrier properties in the newborn infant.

Effect of semipermeable membranes on skin barrier repair following tape stripping.

Reports in the literature suggest that the permeability of a wound dressing to water transport is an important variable in the healing of superficial wounds. Factors that influence skin hydration during barrier repair, therefore, are important in the optimization of wound treatments. In this study, the effects of semipermeable films on human skin following a standardized wound (tape stripping) were evaluated using measurements of transepidermal water loss (TEWL), skin hydration, rate of moisture accumulation, and erythema. Wounds treated with semipermeable films underwent more rapid barrier recovery than either unoccluded wounds or wounds under complete occlusion. Barrier films that produced intermediate levels of skin hydration during recovery produced the highest barrier repair rates. The results support the hypothesis; that semipermeable wound dressings augment barrier repair and skin quality by providing an optimized water vapor gradient during the wound healing process. The choice of wound dressing is discussed within the larger context of the design of vapor-permeable fabrics (smart materials) and the new fields of corneotherapy and comfort science.

In vitro percutaneous absorption of the fragrance ingredient musk xylol.

The percutaneous absorption of the fragrance fixative musk xylol was measured in vitro in human and hairless guinea pig skin. For comparison, musk xylol was applied to skin in an oil-in-water emulsion or the volatile solvent, methanol. After 24 hr, total absorption of musk xylol in hairless guinea pig skin was 55% from the emulsion vehicle and 45% from the methanol vehicle. With human skin, permeation of musk xylol from both vehicles decreased to 22% of the applied dose. When human studies were continued for an additional 6 days after skin surface washing, only 6% of the applied dose remained in skin. The data suggest that most of the absorbed musk xylol in skin at 24 hr will be systemically absorbed in vivo within 1 wk. Throughout the 24-hr absorption study, absorbed musk xylol was not metabolized. A permeability constant for musk xylol permeation through hairless guinea pig skin was determined by a modified procedure for the lipophilic compound. At each time point, some diffusion cells were terminated so that skin and receptor fluid levels could be determined. Under steady-state absorption the permeability constant was 6.86 x 10(-5) cm/hr. The amount of musk xylol penetrating skin from three types of cosmetic products was also calculated on the basis of actual conditions of use. Products that are applied to large areas of the body and remain on the skin for long periods will result in the greatest absorption of musk xylol.

In vitro and in vivo percutaneous absorption of catechol.

The Cosmetic Ingredient Review Expert Panel found insufficient data to conclude that catechol could be used safely in permanent hair dye products. Information was lacking on the extent of oxidation and skin absorption of remaining catechol. In vitro percutaneous absorption studies were conducted in human and rat skin using a consumer permanent hair dye spiked with 0.6% catechol. A 30-min application demonstrated 0.4% of the applied dose was absorbed through human skin and 0.2% through rat skin. The minimal absorption observed was due to the short exposure time and to partial oxidation of catechol by the dye developer. The fate of catechol remaining in rat skin after exposure in vitro and in vivo was investigated with additional absorption studies using catechol in ethanol. At 72 h, 24-h application of 4% catechol resulted in skin absorption of 81% of the applied dose in vitro and 53% in vivo. Skin levels measured at 24 h remained unchanged after 72 h. Therefore the skin reservoir did not contribute to the estimated systemic absorption. A deconvolution technique employed to predict skin absorption using plasma levels from intravenous and dermal administration overestimated in vivo skin absorption due to volatility of catechol in an ethanolic vehicle.

Assessment with the dermal torque meter of skin pliability after treatment of burns with cultured skin substitutes.

The assessment of visco-elastic (V-E) properties in cutaneous scars is critical to reduction of impairment and restoration of function after grafting of excised burns. Cultured skin substitutes (CSS) that consist of autologous keratinocytes and fibroblasts attached to biopolymer substrates are alternatives for permanent closure of excised, full-thickness burns, but assessment of scarring has been subjective. V-E properties of CSS were measured with a Dia-Stron Dermal Torque Meter (DTM 310, Dia-Stron, Ltd, Broomall, Pa), which applies a constant torque (10 mNm) for a fixed interval (10 seconds) and measures rotational deformation and recovery. Parameters of skin deformation were measured in patients (n = 10) after grafting of CSS or meshed skin autograft. Native human skin (NHS) of healthy volunteers (n = 13) served as the control. Skin healed after treatment with CSS or autograft was evaluated for 1 year or longer after grafting. Elastic stretch (Ue), viscous stretch (Uv), total extensibility (Uf), elastic recovery (Ur), total recovery (Ua), and residual plasticity (R) were measured as degrees of rotation, were tested for significance (P < .05) by Student t test comparisons between treatment groups and controls, and were subjected to regression analysis. Assessment of burn scar with the Dermal Torque Meter detected time-dependent increases of all individual parameters of V-E properties for both CSS and autograft during the first year after grafting. At 1 year or later, no statistical differences were found between CSS and autograft for individual parameters, but Ue and Ur for autograft were significantly lower than for NHS. At 1 year or longer, autograft was significantly different from CSS or NHS, with a greater ratio of Uv to Ue, and both graft types had a lower ratio of Ur to Uf than NHS had. These results suggest that instrumental measurement of scar pliability may increase objectivity in assessment of patient recovery and establish an absolute scale for quantitative analysis of V-E properties in skin after grafting of conventional or alternative skin substitutes.

Permanent waving and straightening of hair.

A significant number of consumers use products to curl or straighten their hair. These products function by chemically breaking and reforming keratin disulfide bonds. The most popular waving products contain salts of thioglycolic acid to break the bonds and hydrogen peroxide to reform them. Straighteners generally rely on high alkalinity to break the bonds and reform them with acid. Problems with permanent waving are usually due to overtreatment or undertreatment of the hair rather than allergy or irritation. Straighteners can be irritating because of their high alkalinity and can seriously damage hair if used excessively.

The ability of electrical measurements to predict skin moisturization. I. Effects of NaCl and glycerin on short-term measurements.

Non-invasive methods to evaluate skin hydration by measuring electrical properties are widely used in the cosmetic industry. However, there is still some controversy about factors that affect measurement. For example, concerns have often been expressed about the possible confounding effect of salts, either in the formulation or on the skin. Ionized salts on the skin may increase electrical conductivity and may lead to changes in electrical properties that are not related to increased water content. We have performed a systematic study of the effects of salt, i.e., sodium chloride, and glycerin on the electrical properties of skin as measured by the three most commonly used instruments, the Nova DPM 9003, the Corneometer CM 825, and the Skicon 200. Formulations containing salt from 0-3% and glycerin from 0-10% were tested for their effects at one and two hours after a single application. Salt lowered the readings in the absence of glycerin and increased the reading in the presence of glycerin. For all three instruments, there was a linear correlation between the measurement and the glycerin level in the presence or absence of salt.

The ability of electrical measurements to predict skin moisturization. II. Correlation between one-hour measurements and long-term results.

We investigated the ability of short-term (one-hour) electrical measurements with three different commonly used instruments to predict the effects of long-term treatment with glycerin-containing formulations on moderately dry leg skin. We report the moisturizing effects of glycerin on healthy female adult skin in a two-week study as measured by electrical conductance and capacitance, transepidermal water loss (TEWL), and clinical grading of skin dryness. The test formulations contained 1.5% NaCl and levels of glycerin from 0% to 15%. Results obtained with a smaller cohort of ten subjects, one hour after treatment, were predictive of moisturizing efficacy in the two-week period among twenty subjects with dry leg skin. Our results show that single application tests can be predictive of longer-term results with humectant-based moisturizers and that electrical measurements of skin conditions correlate well with skin grades.