A controlled forearm washing ex vivo method for assessing the impact of personal cleansing products on skin's acid mantle properties and antimicrobial defence against transient bacteria.

BACKGROUND: An important trend in the personal care industry involves the development of advanced personal cleaning products that not only provide skin mildness but support skin's acid mantle properties and skin's natural antimicrobial defence function. OBJECTIVE: The objective of this study was to develop a controlled forearm washing ex vivo method for assessing the impact of personal cleansing products on skin's acid mantle properties and antimicrobial defence against transient bacteria. METHODS: We developed a controlled forearm washing ex vivo method (ex vivo NET method) to compare the impact of two representative personal cleansing products on skin's acid mantle properties and antimicrobial defence against transient bacteria: one was a low-pH skin cleanser, and the other was high-pH soap cleanser. Skin pH was measured at baseline and 4 h after the product application. Concurrently, D-squame tape stripping procedure was followed to sample the stratum corneum surface layers. Then, two selected transient bacteria, Staphylococcus aureus and Escherichia coli, were inoculated onto the D-squame tapes and incubated under controlled conditions, respectively. The residual bacteria counts can provide an objective measure of skin's acid mantle properties against transient bacteria. Results from the ex vivo NET method were compared with the traditional in vivo cup-scrub RET method. RESULTS: The skin pH was significantly lower 4 h after washing the forearm with the low-pH cleanser versus the high-pH soap, consistent with literatures. Interestingly, the skin surface washed by the low-pH cleanser showed significantly higher hostility against representative transient bacteria as demonstrated by the lower counts of S. aureus by 1.09 log and E. coli by 0.6 log versus the high-pH soap based on the ex vivo NET method. Results from the ex vivo NET method were further supported by the traditional in vivo RET method which also showed the skin washed by the low-pH cleanser had significantly lower counts of S. aureus and E. coli versus the high-pH soap. CONCLUSIONS: The skin's acid mantle properties and antimicrobial defence can be directly impacted by the personal cleansing products. The low-pH skin cleanser works better than the high-pH soap for supporting skin's acid mantle properties and antimicrobial defence against transient bacteria. Results from the ex vivo NET method are consistent with the in vivo RET method. It is important that the ex vivo NET method offers many advantages since it is quicker to run with higher throughput and has better safety without the constraint of inoculating harmful microorganisms onto the human subjects.

CONTEXTE: Une tendance importante du secteur des soins personnels est de développer des produits d'hygiène personnelle sophistiqués qui non seulement rendent la peau plus douce, mais favorisent également les propriétés du manteau acide de la peau et la fonction de défense antimicrobienne naturelle de la peau. OBJECTIF: L'objectif de cette étude était de développer une méthode ex vivo de lavage contrôlé des avant-bras pour évaluer l'impact des produits d'hygiène personnelle sur les propriétés du manteau acide de la peau et la défense antimicrobienne contre les bactéries transitoires. MÉTHODES: Nous avons développé une méthode ex vivo de lavage contrôlé des avant-bras (méthode NET ex vivo) pour comparer l'impact de deux produits d'hygiène personnelle représentatifs sur les propriétés du manteau acide de la peau et la défense antimicrobienne contre les bactéries transitoires: d'une part un nettoyant pour la peau à pH faible, d'autre part un savon nettoyant à pH élevé. Le pH de la peau a été mesuré à l'entrée dans l'étude et quatre heures après l'application du produit. Parallèlement, une procédure de stripping par ruban adhésif D-Squame a été suivie pour prélever des couches de surface de la couche cornée. Ensuite, deux bactéries transitoires sélectionnées, S. aureus et E. coli, ont été inoculées sur les rubans adhésifs D-Squame et incubées dans des conditions contrôlées, respectivement. Le nombre de bactéries résiduelles peut fournir une mesure objective des propriétés du manteau acide de la peau contre les bactéries transitoires. Les résultats de la méthode NET ex vivo ont été comparés à la méthode RET in vivo traditionnelle par coupe-grattage. RÉSULTATS: Le pH de la peau était significativement inférieur quatre heures après le lavage des avant-bras avec le nettoyant à pH faible en comparaison avec le savon à pH élevé, conformément à la littérature. Il est intéressant de noter que la surface de la peau lavée au moyen du nettoyant à pH faible présentait une hostilité significativement plus élevée contre les bactéries transitoires représentatives, comme démontré par le nombre inférieur de S. aureus de 1,09 log et d'E. coli de 0,6 log, en comparaison avec le savon à pH élevé, sur base de la méthode NET ex vivo. Les résultats de la méthode NET ex vivo ont été encore par la méthode RET in vivo traditionnelle, laquelle a également démontré que la peau lavée à l'aide du nettoyant à pH faible présentait des nombres significativement plus faibles de S. aureus et d'E. coli que celle lavée à l'aide du savon à pH élevé. CONCLUSIONS: Les propriétés du manteau acide de la peau et la défense antimicrobienne peuvent être directement affectées par les produits d'hygiène personnelle. Le nettoyant de la peau à pH faible fonctionne mieux que le savon à pH élevé pour ce qui est de favoriser les propriétés du manteau acide de la peau et la défense antimicrobienne contre les bactéries transitoires. Les résultats de la méthode NET ex vivo sont cohérents avec la méthode RET in vivo. Il est important de noter que la méthode NET ex vivo offre de nombreux avantages étant donné qu'elle est plus rapide à exécuter avec une capacité plus élevée et offre une meilleure sécurité sans la contrainte d'inoculer des micro-organismes nocifs à des sujets humains.

Effects of petrolatum, a petrolatum depositing body wash and a regular body wash on biomarkers and biophysical properties of the stratum corneum.

BACKGROUND: An important trend in the personal care industry involves the development of body wash products that not only clean the skin without damage but deposit conditioning ingredients to improve skin barrier function. OBJECTIVE: The objective of this study was to develop skin biomarker measures to quantify the treatment effects of body wash products. METHODS: We employed analysis of structural proteins (keratin 1,10,11 and involucrin), a natural moisturizing factor (pyrrolidone carboxylic acid) and an inflammatory mediator (IL-1ra/IL-1α) from adhesive discs with dry skin grading, TEWL and capacitance measurements to compare the effects of direct application of petrolatum, a high petrolatum depositing body wash, and a regular body wash on dry leg skin in a standard leg-wash treatment protocol. RESULTS: High depositing body wash and petrolatum had positive effects on stratum corneum barrier function as judged by biomarker analysis, biophysical measurements and skin grading compared to the regular body wash product. CONCLUSIONS: The results clearly indicate that a combination of biomarker and biophysical property measurements is effective for determining the skin benefits of moisturizing body wash products.

CONTEXTE: Une tendance importante dans l'industrie des soins personnels inclut le développement de produits de lavage corporel qui non seulement nettoient la peau sans l'endommager, mais déposent des ingrédients de traitement pour améliorer la fonction de la barrière cutanée. OBJECTIF: L'objectif de cette étude était de développer des mesures de biomarqueurs cutanés permettant de quantifier les effets du traitement des produits de lavage corporel. MÉTHODES: Nous avons utilisé l'analyse de protéines structurelles (kératine 1,10,11 et involucrine), un facteur hydratant naturel (acide carboxylique de pyrrolidone) et un médiateur inflammatoire (IL-1ra/IL-1a) provenant de disques adhésifs avec cotation de la sécheresse cutanée, mesures de perte d'eau transépidermique (transepidermal water loss, TEWL) et de capacitance pour comparer les effets de l'application directe de vaseline, d'un produit de lavage corporel avec dépôt élevé de vaseline et d'un produit de lavage corporel ordinaire sur la peau sèche des jambes, dans un protocole de traitement de lavage des jambes standard. RÉSULTATS: Le produit de lavage corporel à dépôt élevé et la vaseline avaient des effets positifs sur la fonction de barrière de la couche cornée, comme évalué par l'analyse des biomarqueurs, les mesures biophysiques et la cotation de la peau, comparé au produit de lavage corporel ordinaire. CONCLUSIONS: Les résultats indiquent clairement qu'une combinaison de mesures des biomarqueurs et des propriétés biophysiques est efficace pour déterminer les bienfaits pour la peau des produits de lavage corporel hydratants.

Skin benefits of moisturising body wash formulas for children with atopic dermatitis: A randomised controlled clinical study in China.

BACKGROUND: It acknowledged that skin care is an important part of atopic dermatitis therapy. However, clinical evidences are limited for the best bathing practices, especially the skin health performance of cleansing products on children's atopic dermatitis skin. METHODS: A randomised controlled clinical study was conducted in China among 4- to 18-year-old children with mild-to-moderate atopic dermatitis to evaluate the skin health effect of three cleansing systems (a mild synthetic bar, an ultra-mild body wash with lipids, and an ultra-mild body wash with lipids and zinc pyrithione) by measuring SCORing of Atopic Dermatitis (SCORAD), consumption of topical corticosteroid and the characteristics of microbiome. RESULTS: Increased Staphylococcus aureus abundance and decreased microbial diversity were observed in atopic dermatitis lesion sites compared with healthy control sites. After 4 weeks of treatment, all three treatments showed clinically important improvement from baseline in SCORAD. Four-week corticosteroid consumption was significantly lower for the two body wash groups than the bar group. A significant decrease in S. aureus abundance and increase in microbial diversity were observed in the lesion sites for the two body wash formulas, while the microbial diversity was statistically insignificant for the mild cleansing bar group. However, there were no incremental benefits provided by the body wash formulas based on the assessment of SCORAD. CONCLUSIONS: These results demonstrated the safety and efficacy of using the investigational body wash formulas with lipids in reducing the needs for corticosteroid and improving the healthy composition of skin microbiome vs. the mild synthetic bar soap.

MCR Approach Revealing Protein, Water, and Lipid Depth Profile in Atopic Dermatitis Patients' Stratum Corneum via in Vivo Confocal Raman Spectroscopy.

Confocal Raman has been widely used for measuring the water concentration profile inside skin to calculate clinical end points, such as stratum corneum thickness. In this article, multivariate curve resolution was applied to resolve the pure components contained in high frequency (2500-4000 cm-1) in vivo confocal Raman data. Three components were identified by comparing with reference spectra of materials in skin. These three components are water, protein, and lipid. The score values associated with these three components were transformed to mass ratio by leveraging the response factors for protein and lipid in a calibration model utilizing the pure material spectra. The concentration profiles for protein and lipid as a function of depth across the stratum corneum are utilized as new clinical end points. Results from an in vivo study with individuals who experience atopic dermatitis symptoms successfully demonstrated a statistical difference between Raman spectra from nonlesion and lesion skin sites. Trends in the depth profiles of the skin components are consistent with previous literature reports.

In Vitro Penetration of Petrolatum in Stratum Corneum from Bodywash Formulation.

Petrolatum is a mixture of hydrocarbons that is widely used as a moisturizer. It is incorporated in bodywash formulations to help hydrate and maintain healthy skin appearance. The aim of this study was to investigate skin deposition and penetration of petrolatum from an experimental bodywash system consisting of petrolatum in vitro. Experiments were performed using cadaver split-thickness skin and Franz diffusion cells. Radiolabeled 14C-dotriacontane (C32-alkane) was used as a model permeant for petrolatum. The bodywash was applied on the skin and subsequently rinsed. At predetermined time points, the skin was wiped to remove the residual material on the surface, and tape-stripping was performed. Petrolatum was observed to deposit from the bodywash when applied on split-thickness skin with simulated rinsing. Petrolatum then penetrated into the stratum corneum and was detected at the depth of 12 tape-stripping and in the epidermis. The bodywash formulation could provide significant deposition and penetration of petrolatum into the stratum corneum at 1-72 hours postapplication.

Effects of season stratum corneum barrier function and skin biomarkers.

The skin on the lower legs of 25 female subjects was evaluated first in the winter, and then again in the summer of the same subjects. Barrier function was determined by measuring transepidermal water loss (TEWL), and skin hydration and dryness were evaluated by electrical measurements (Corneometer ® CM825) and visual grading. Stratum corneum (SC) was sampled using 10 sequential D-Squame sampling discs and analyzed for 2-pyrrolidone-5-carboxylic acid (PCA), keratin-1,10,11, interleukin 1α (IL-1α), interleukin 1 receptor antagonist (IL-1ra), selected ceramides, cholesterol, cholesterol sulfate, and selected free fatty acids. TEWL as well as the visual dryness grades were significantly lower in the summer while hydration was higher. PCA was significantly higher in the summer as were the keratins. The ratio IL-1ra:IL-1α, an indicator of skin inflammation, was significantly lower in the summer. The amount of protein removed by the tape strips was also significantly lower in summer indicating better SC cohesion. Among the SC lipids measured, total ceramides, individual ceramides, total fatty acids, and cholesterol were higher in summer compared to winter. Stearic acid and cholesterol sulfate were not significantly different between winter and summer.

A sequential tape stripping approach for the assessment of the impact of personal cleansing products on the stratum corneum surface layers' acid mantle properties and antimicrobial defense.

BACKGROUND: Stratum corneum (SC) plays a critical role in skin barrier function for protection and defense in nature. The acidic skin pH, which is also known as the acid mantle, is very important in fighting against outer environmental threats, especially, bacteria. Furthermore, recent research has shown that the transient bacteria could potentially penetrate into deeper layer of the SC down to a few micrometers while posing an additional threat to the deeper layers of the skin. AIM: To develop a sequential tape stripping method for assessing the impact of personal cleansing product on the SC surface layers' acid mantle properties and antimicrobial defense against transient bacteria. METHODS: Fifty-five subjects were recruited. High pH soap-based Product 1 and low pH synthetic surfactant-based Product 2 were applied on the left and right forearms of each subject. Sequential tape stripping was performed on the same spots to access multiple layers of the skin SC. Both antimicrobial defense property and skin pH of different skin layers were evaluated at baseline and 12 h after treatment. RESULTS: The skin's antimicrobial defense was significantly higher 12 h after treatment of the low pH Product 2 as compared to the treatment of high pH Product 1. In fact, this trend was consistent across all three skin layers (Layer 1 to Layer 3) as measured in this study (p < 0.01). Furthermore, the skin surface pH of Layer 1 and Layer 3 were also lower 12 h after the treatment of low pH Product 2 as compared to that of the high pH Product 1 (p < 0.01). CONCLUSION: The results of this investigation demonstrated the benefits of 12-h long lasting and deeper protection of SC acid mantle properties and antimicrobial defense using a low pH skin cleansing product as compared to a high pH product.

Association Between Skin Acid Mantle, Natural Moisturizing Factors, and Antibacterial Activity Against S. aureus in the Stratum Corneum.

Purpose: The skin has evolved a system to prevent pathogenic microorganism colonization and infection. This study examined the role of natural moisturizing factors (NMFs) and skin pH on Staphylococcus aureus (S. aureus) growth and colonization on the human stratum corneum (SC). Study Population and Methods: A survey study with 82 female participants was performed. Participants maintained their daily hygiene routine, except for refraining from using leave-on products on their forearms on the day of the test. Skin sampling was performed using adhesive tapes. An ex vivo method was developed to study the viability and growth of S. aureus on human SC sampled from normal skin. NMFs, including pyrrolidone carboxylic acid (PCA), urocanic acid (UCA), histidine, and proline in SC samples, were measured by liquid chromatography with tandem mass spectrometry. The impact of PCA and UCA on S. aureus growth and metabolic activity was measured by optical density and isothermal microcalorimetry, respectively. Results: Heterogeneity of S. aureus viability on human SC samples was observed. Skin pH showed a significant negative association (p<0.05) with SC antibacterial activity in the ex vivo assay. One unit of skin pH decrease corresponded to 68.1% of S. aureus cell death. The levels of PCA and histidine were significantly negatively associated (p<0.05) with skin pH. The addition of 5 mM and 10 mM PCA significantly inhibited S. aureus growth by approximately 25% at 20 hours and reduced its metabolic activity in vitro. Conclusion: The results indicate that PCA, one of the NMFs in human skin, plays an important role in regulating the human skin acid mantle in vivo and contributes to antibacterial activity against S. aureus.

An improved human skin explant culture method for testing and assessing personal care products.

BACKGROUND: Cultured human skin models have been widely used in the evaluation of dermato-cosmetic products as alternatives to animal testing and expensive clinical testing. The most common in vitro skin culture approach is to maintain skin biopsies in an airlifted condition at the interface of the supporting culture medium and the air phase. This type of ex vivo skin explant culture is not, however, adequate for the testing of cleansing products, such as shampoos and body washes. One major deficiency is that cleansing products would not remain confined on top of the epidermis and have a high chance of running off toward the dermal side, thus compromising the experimental procedure and data interpretation. MATERIALS AND METHODS: Here, we describe an improved ex vivo method for culturing full-thickness human skin for the effective testing and evaluation of skin care products by topical application. RESULTS: This newly developed ex vivo human skin culture method has the ability to maintain healthy skin tissues for up to 14 days in culture. Importantly, the model provides a quick and safe way to evaluate skin care products at different time points after single or repetitive topical applications using a combined regimen of leave-on and wash-off. We found that the results obtained using the new skin culture method are reproducible and consistent with the data collected from clinical testing. CONCLUSION: Our new ex vivo skin explant method offers a highly efficient and cost-effective system for the evaluation and testing of a variety of personal care products and new formulations.

Resolving Water, Proteins, and Lipids from In Vivo Confocal Raman Spectra of Stratum Corneum through a Chemometric Approach.

Development of this in vivo confocal Raman spectroscopic method enables the direct measurement of water, proteins, and lipids with depth resolution in human subjects. This information is very important for skin-related diseases and characterizing skin care product performance. This protocol illustrates a method for confocal Raman spectra collection and the subsequent analysis of the spectral dataset leveraging chemometrics. The goal of this method is to establish a standard protocol for data collection and provide general guidance for data analysis. Preprocessing (e.g., removal of outlier spectra) is a critical step when processing large datasets from clinical studies. As an example, we provide guidance based on prior knowledge of a dataset to identify the types of outliers and develop specific strategies to remove them. A principal component analysis is performed, and the loading spectra are compared with spectra from reference materials to select the number of components used in the final multivariate curve resolution (MCR) analysis. This approach is successful for extracting meaningful information from a large spectral dataset.

A Microbiome-Based Index for Assessing Skin Health and Treatment Effects for Atopic Dermatitis in Children.

A quantitative and objective indicator for skin health via the microbiome is of great interest for personalized skin care, but differences among skin sites and across human populations can make this goal challenging. A three-city (two Chinese and one American) comparison of skin microbiota from atopic dermatitis (AD) and healthy pediatric cohorts revealed that, although city has the greatest effect size (the skin microbiome can predict the originated city with near 100% accuracy), a microbial index of skin health (MiSH) based on 25 bacterial genera can diagnose AD with 83 to ∼95% accuracy within each city and 86.4% accuracy across cities (area under the concentration-time curve [AUC], 0.90). Moreover, nonlesional skin sites across the bodies of AD-active children (which include shank, arm, popliteal fossa, elbow, antecubital fossa, knee, neck, and axilla) harbor a distinct but lesional state-like microbiome that features relative enrichment of Staphylococcus aureus over healthy individuals, confirming the extension of microbiome dysbiosis across body surface in AD patients. Intriguingly, pretreatment MiSH classifies children with identical AD clinical symptoms into two host types with distinct microbial diversity and treatment effects of corticosteroid therapy. These findings suggest that MiSH has the potential to diagnose AD, assess risk-prone state of skin, and predict treatment response in children across human populations.IMPORTANCE MiSH, which is based on the skin microbiome, can quantitatively assess pediatric skin health across cohorts from distinct countries over large geographic distances. Moreover, the index can identify a risk-prone skin state and compare treatment effect in children, suggesting applications in diagnosis and patient stratification.