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The epidermis is an essential organ for life by retaining water and as a protective barrier. The epidermis is maintained through metabolism, in which basal cells produced from epidermal stem cells differentiate into spinous cells, granular cells and corneocytes, and are finally shed from the epidermal surface. This is epidermal turnover, and with aging, there is a decline in epidermis function. Other factors that may affect epidermal turnover include ultraviolet damage and genetic factors. These genetic factors are of particular interest as little is known. Although recent skin‐focused genome‐wide association studies (GWAS) have been conducted, the genetic regions associated with epidermal turnover are almost uninvestigated. Therefore, we conducted a GWAS on epidermal turnover in the Japanese population, using the corneocyte area, which correlates to the rate of epidermal turnover, as an indicator. As a result, rs2278431 (p = 1.29 × 10−7) in 19q13.2 was associated with corneocyte size. Furthermore, eQTL analysis suggested that rs2278431 was related to the SPINT2 gene. In addition, SPINT2 knockdown studies using epidermal keratinocytes revealed that SPINT2 is involved in keratinocyte proliferation and in corneocyte size regulation in reconstructed epidermis. These results suggest that rs2278431 is involved in the expression of SPINT2 and affects epidermal turnover. [ABSTRACT FROM AUTHOR]

Background: ε‐Poly‐L‐lysine (PLL) is a cationic polymer consisting of 25 to 35 L‐lysine residues that adheres to the surface of skin as well as hair. However, the properties of PLL regarding its adhesion to the skin remain to be elucidated. In this study, we examined the staining of stratum corneum (SC) with fluorescence‐labeled PLL and explored its relationship with skin condition. Materials and methods: Alexa Fluor 488‐labeled PLL (AF‐PLL) was reacted with tape‐stripped stratum corneum (SC), and the staining properties were monitored by fluorescence microscopy. Clinical study was performed by measuring the water content of the cheek SC and transepidermal water loss (TEWL), and the tape‐stripped SC was subjected to staining with AF‐PLL. Results: AF‐PLL staining of the SC was inhibited at acidic pH or by the addition of high concentration of salt solution, suggesting the involvement of ionic interaction between PLL and the SC, at least in part. The AF‐PLL staining was inhibited by unlabeled PLL or various alkyl amines, but not by L‐lysine monomer. AF‐PLL staining was observed inside the corneocytes as well as surrounding cornified envelope. Clinical study revealed that AF‐PLL staining intensity of the SC was negatively correlated with its water content and positively correlated with its TEWL. Conclusion: PLL can efficiently adhere to SC and AF‐PLL staining of SC can be applied to evaluate skin conditions. [ABSTRACT FROM AUTHOR]

Mitochondria have their own DNA (mtDNA). Genetic variants are likely to accumulate in mtDNA, and its base substitution rate is known to be very fast, 10–20 times faster than that of nuclear DNA. For this reason, mtSNPs (mitochondrial genome single nucleotide polymorphisms) are frequently detected in mtDNA. Several thousands of copies of mtDNA are considered to be present in a cell, and variants that have occurred in mtDNA are expected to markedly affect the intracellular energy production system and ROS (reactive oxygen species) kinetics. Therefore, recently, mtSNPs have come to be considered very important as a determinant of the individual constitution such as the life‐span and disease susceptibility. In this study, we searched for mtSNPs that affect the individual corneocyte size using samples from 358 Japanese women. As a result, mtSNPs 10609C and 12406A were found to be significantly related to the corneocyte size in the outermost layer of the epidermis. There have been a large number of reports concerning the association between mtSNPs and individual constitution, but little evaluation of their relationships with epidermal properties has been made. The results of the present study first suggested that mtSNPs may affect the epidermal properties in Japanese women. [ABSTRACT FROM AUTHOR]

Summary: Background: Skin hydration is generally assessed using the parameters of skin surface water content (SWC) and trans‐epidermal water loss (TEWL). To date, few studies have characterized skin conditions using correlations between skin hydration parameters and corneocyte parameters. Aims: The parameters SWC and TEWL allow the classification of skin conditions into four distinct Groups. The purpose of this study was to assess the characteristics of skin conditions classified by SWC and TEWL for correlations with parameters from corneocytes. Methods: A human volunteer test was conducted that measured SWC and TEWL. As corneocyte‐derived parameters, the size and thick abrasion ratios, the ratio of sulfhydryl groups and disulfide bonds (SH/SS) and CP levels were analyzed. Results: Volunteers were classified by their median SWC and TEWL values into 4 Groups: Group I (high SWC/low TEWL), Group II (high SWC/high TEWL), Group III (low SWC/low TEWL), and Group IV (low SWC/high TEWL). Group IV showed a significantly smaller size of corneocytes. Groups III and IV had significantly higher thick abrasion ratios and CP levels. Group I had a significantly lower SH/SS value. The SWC/TEWL value showed a decline in order from Group I to Group IV. Conclusion: Groups classified by their SWC and TEWL values showed characteristic skin conditions. We propose that the SWC and TEWL ratio is a comprehensive parameter to assess skin conditions. [ABSTRACT FROM AUTHOR]

The precise chain length of the ceramide sphingoid bases and free fatty acids: So far, no changes in ceramide chain lengths have been reported for dry skin on the legs unlike facial SC. Keywords: skin barrier; skin physiology/structure; stratum corneum; corneocyte; ceramide; moisturization EN skin barrier skin physiology/structure stratum corneum corneocyte ceramide moisturization 269 271 3 04/12/21 20210401 NES 210401 Recently we published an article "Targeted dry skin treatment using a multifunctional topical moisturizer", https://doi.org/10.1111/ics.12680, which was as always corrected and reviewed by expert reviewers of the journal. The lowered levels of ceramides generally: Stettler I et al i . report increased levels of ceramide NH and associated increased numbers and length of lipid lamellae in the central layers of the SC. Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function. [Extracted from the article]

Background: The skin barrier protects the organism against exogenous stressors and simultaneously prevents excessive water loss. While the delicate regulation of skin barrier is not completely understood, morphological and histological evaluation remain key features of clinical investigations. Here, we extended the phenotypic perspective down to the nanoscale. Methods: Corneocyte samples were obtained non-invasively by a standard tape stripping procedure from 21 indviduals. Scanning electron (SEM) and atomic force microcopy (AFM) were used to record nanoscale topography. Circular nanoobjects were identified and these were quantitated through computer vision. Results: Typical dimensions of 273 nm height and 305 nm width. We showed that their density does not correlate to age or pigmentation in healthy subjects, but that they were clearly elevated in corneocytes from patients with atopic dermatitis, a common inflammatory skin condition. Conclusion: The presence of these corneocyte-nanostructures might be used as a diagnostic parameter for skin disorders - even in cases below a clinical threshold. [ABSTRACT FROM AUTHOR]

Synopsis Recently, we developed a biophysical approach to characterize in vivo facial cheek skin as a function of stratum corneum ( SC) depth, barrier function and during a 24-h recovery period. The current study extends this work and characterizes the human facial cheek after barrier challenge and, for the first time, facial SC barrier recovery over a 4-week period. Changes in the corneocyte size over the 4-week recovery period, and correlations with changes in Trans-Epidermal Water Loss ( TEWL) were monitored. This approach allows complete characterization of SC barrier function after a full biological regeneration of the SC barrier following tape stripping. The structural and compositional changes in facial cheek were investigated using Attenuated Total Reflectance-Fourier Transform Infra Red ( ATR- FTIR) spectroscopy, tape stripping, TEWL measurements and image analysis combined with optical microscopy to characterize the SC depth profile during the tape stripping stress and over 4-week recovery period. TEWL increased significantly from baseline after sequential tape stripping. Corneocyte size decreased with successive tape stripping. An inverse direct correlation was determined between TEWL and corneocyte surface area. After 4 weeks, the corneocyte size and TEWL for the facial cheek recovered 100% from the tape stripping procedure. The in vivo ATR- FTIR data demonstrated that lipid and sebum components on the surface of the facial cheek SC recovered within 24 h post tape stripping, whereas protein (Amide II) and water components recovered after 1 week. [ABSTRACT FROM AUTHOR]

The skin is the largest organ of the human body and its functions include protection, thermoregulation sensation and secretion. Significant advances in our understanding of how the morphology and physiology of the skin contribute to the skin's barrier role have been achieved in recent years. The aim of this review is to summarize the principal approaches which have been used to assess variation in skin barrier function with anatomic site, age, gender, and ethnicity. The methods discussed include trans-epidermal water loss (TEWL) measurement, assessment of corneocyte size, response to vasoactive compounds and attenuated total reflectance Fourier transform infrared (ATR-FTIR) interrogation of skin. The utility of the various methods is considered and the most important findings in the literature to date are highlighted. [ABSTRACT FROM AUTHOR]

Background/purpose: Atomic force microscopy (AFM) is a novel technique for skin characterization. Objectives: To develop AFM tests for characterization of the outermost epidermis layer, corneocytes. As an example, the effect of moisturizer on the corneocyte properties is studied. Methods and materials: Topology, rigidity, and friction (between individual corneocytes and AFM probe) of the top layer of corneocytes were measured by means of Veeco DM3100 AFM. Quench™ moisturizing cream was applied daily on the forearm of five volunteers for a period of 9 days. The skin flakes were collected before and after the treatment using Cuderm tape strips. No additional treatment of flakes was performed before the measurements. Results: A protocol for the AFM study of corneocytes is developed. After the treatment, we observed overall smoothening of the corneocyte surface, an increase of friction, and a decrease of rigidity (the Young modulus). Conclusion: AFM can be used as a very sensitive tool for early detection of changes in corneocytes. [ABSTRACT FROM AUTHOR]

Synopsis Between the two different kinds of the skin covering the body, the glabrous skin is found only on the palmo-plantar surface because of its rather simple function to protect the underlying living tissue with its remarkably thick stratum corneum (SC) from strong external force and friction. Thus, its barrier function is extremely poor. In contrast, the hair-bearing skin covers almost all over the body surface regardless of the presence of long hair or vellus hair. In regard to its SC, many dermatologists and skin scientists think that it is too thin to show any site-specific differences, because the SC is just present as an efficient barrier membrane to protect our body from desiccation as well as against the invasion by external injurious agents. However, there are remarkable regional differences not only in the living skin tissue but also even in such thin SC reflecting the function of each anatomical location. These differences in the SC have been mostly disclosed with the advent of non-invasive biophysical instruments, particularly the one that enables us to measure transepidermal water loss (TEWL), the parameter of the SC barrier function, and the one that evaluates the hydration state of the skin surface, the parameter of the water-holding capacity of the SC that brings about softness and smoothness to the skin surface. These in vivo instrumental measurements of the SC have disclosed the presence of remarkable differences in the functional properties of the SC particularly between the face and other portions of the body. The SC of the facial skin is thinner, being composed of smaller layers of corneocytes than that of the trunk and limbs. It shows unique functional characteristics to provide hydrated skin surface but relatively poor barrier function, which is similar to that observed in retinoid-treated skin or to that of fresh scar or keloidal scars. Moreover, there even exist unexpected, site-dependent differences in the SC of the facial skin such as the forehead, eyelid, cheek, nose and perioral regions, although each location occupies only a small area. Between these locations, the cheek shows the lowest TEWL in contrast to the perioral region that reveals the highest one. Moreover, these features are not static but change with age particularly between children and adults and maybe also between genders. Among various facial locations, the eyelid skin is distinct from others because its SC is associated with poor skin surface lipids and a thin SC cell layer composed of large corneocytes that brings about high surface hydration state but poor barrier function, whereas the vermillion borders of the lips that are covered by an exposed part of the oral mucosa exhibit remarkably poor barrier function and low hydration state. Future studies aiming at the establishment of the functional mapping in each facial region and in other body regions will shed light on more delicate site-dependent differences, which will provide us important information in planning the strategy to start so called tailor-made skin care for each location of the body. [ABSTRACT FROM AUTHOR]

Background/purpose: The eyelid constitutes a unique area on the face because of its soft, smooth and thin skin distinct from that of other facial portions. Its softness facilitates their easy compliance to blinking movement, which is indispensable to protect the wet surface of the eyeball. Moreover, the skin of the eyelid does not show any prominent follicular orifices or an oily appearance even in adults. Despite such uniqueness, its biophysical characteristics have remained unclear as compared with other facial skin. Methods: We conducted non-invasive instrumental measurements on the skin of the upper eyelid of 22 healthy Japanese adults in comparison with those of the adjacent facial skin, i.e. the cheek and nose. Additionally, we examined 10 adult patients with atopic dermatitis (AD) whose facial skin remained clinically free from skin lesions for at least 2 months. Results: The eyelid skin showed high transepidermal water loss like other facial skin. Its skin surface hydration state was as high as that of the adjacent skin, despite the fact that the eyelid skin revealed extremely low amounts of surface lipids unlike its neighboring skin regions. However, in contrast to small corneocytes found in other facial areas, the corneocytes of the eyelid skin displayed a significantly larger surface size, suggesting that slow turnover of its stratum corneum (SC) takes place to allow sufficient maturation of the corneocytes, enabling them to exert efficient water-binding capacity. Its pH tended to be higher than that of the adjacent skin. Its superficial blood flow was significantly higher than that of others, although skin color assessment showed lower color values for redness than those of the other facial skin sites. In clinically non-lesional skin of adult AD patients, we found increased blood circulation and a higher parameter for redness, suggesting the presence of invisible mild inflammation in the dermis even long after subsidence of visible inflammatory changes. Conclusion: Our present biophysical findings suggest that, although the eyelid skin is poor in surface lipids, its extraordinary large superficial corneocytes play an important role in maintaining sufficient hydration state of its skin surface to keep it soft and flexible, enabling its good compliance with the blinking movement. [ABSTRACT FROM AUTHOR]

Synopsis Dandruff is a common scalp disorder affecting almost half of the postpubertal population of any ethnicity and both genders. It may, however, represent a stubborn esthetical disturbance often source of pruritus. Skin biocenosis, in particular the Malassezia spp. flora, plays a key aetiologic role, in combination with the unusual capacity of some corneocytes to be coated by these yeasts. Substantial evidence indicates that keratinocytes play an active role in the generation and expression of immunopathological reactions. This is probably the case in dandruff. Upon stimulation of a critical colonization of corneocytes by Malassezia yeasts, the release of pro-inflammatory mediators is increased. This could lead to the subclinical microinflammation present in dandruff. In seborrheic dermatitis, local deposits of immunoglobulins and the release of lymphokines are responsible for the recruitment and local activation of leukocytes leading to the eventual amplification of the inflammatory reaction. Some ancillary non-microbial causes of dandruff may operate through physical or chemical irritants. Many methods have been described for rating dandruff. Our favourite tools are clinical examination and squamometry. Dandruff can precipitate telogen effluvium and exacerbate androgenic alopecia. Antidandruff formulations exhibiting some direct or indirect anti-inflammatory activity can improve both dandruff and its subsequent hair cycle disturbance. [ABSTRACT FROM AUTHOR]

Silicon image sensor (SIS) technology was recently introduced as an innovative tool (SkinChip®, L'Oréal) providing sensitive imaging of the skin capacitance. This method can detect discrete focal variations in skin surface hydration, and thus early discrete manifestations of skin irritation induced by surfactants. In the present in vivo study, 2 neat and diluted shampoos, and 5% and 10% sodium laurylsulfate solutions were tested on human skin. Each surfactant solution was gently rubbed on the skin using wet hair wicks mimicking the casual use of a shampoo on the scalp. Clinical and SIS evaluations were carried out. In addition, the same products were tested using the ex vivo corneosurfametry bioassay performed on human stratum corneum (SC) harvested by cyanoacrylate skin surface strippings. The colourimetric index of mildness (CIM) was measured on these samples. The product reactivity with the SC was recognized by darker skin capacitance images, and by both lowered SkinChip®-generated values and lowered CIM values. The extent in changes varied according to the nature of the test products and their concentrations. The SkinChip® image changes likely corresponded to the acute surfactant-induced water swelling of the corneocytes. Skin capacitance imaging and corneosurfametry allow to disclose discrete surfactant-induced alterations of corneocytes. [ABSTRACT FROM AUTHOR]

Abstract An optimized system of computerized image analysis was used to investigate variations in the adherence of Staphylococcus intermedius to canine corneocytes from four different breed groups and six different anatomical sites. S. intermedius showed significantly greater adherence to the head and neck compared with the dorsum, but adherence to the limb, axilla and groin did not differ from other sites. Furthermore, there was significantly greater adherence of S. intermedius to corneocytes from the dorsum, forelimb, axilla and groin of Boxers and Bull Terriers than Spaniels and Hounds. S. intermedius , and also Pseudomonas aeruginosa , exhibited abundant adherence, which was significantly greater than Staphylococcus aureus , Streptococcus canis , Klebsiella pneumoniae and Escherichia coli. In addition, S. intermedius adherence demonstrated a sigmoid dose–response curve with increasing bacterial concentration. These results suggest that S. intermedius adheres to canine corneocytes by a specific receptor–ligand interaction and adheres to the skin of some breeds more avidly than others. However, variations in adherence between body regions would not account for the predilection sites of canine bacterial pyoderma. [ABSTRACT FROM AUTHOR]

The assessment of many aspects of the structure and biological dynamics of the stratum corneum can be conducted using calibrated stripping with adhesive-coated discs (SACD). Squamometry entails staining SACD samples with a toluidine blue-basic fuschsin ethanol-based solution and reading the colorimetric variable Chroma C* representing the squamometry index. Four main variants of squamometry index have been designed so far. Squamometry X refers to the assessment of xerosis and any scaly condition. Squamometry L explores the intercorneocyte cohesiveness impaired by ultraviolet light. Squamometry R evaluates stratum corneum renewal and squamometry S assesses the effect of surfactants on corneocyte integrity. This latter variant is related to, although not similar to, the ex-vivo corneosurfametry bioassay. All squamometry tests are rapid, reliable, sensitive and cheap. [ABSTRACT FROM AUTHOR]

Skin does not react in an identical way to the action of chemicals over all anatomic sites. Accordingly, distinct regional differences have been described in relation to irritancy. The present study assesses the regional variations of stratum corneum (SC) reactivity to 3 proprietary antiseptic solutions (povidone iodine (PVP-I), 70 mg/ml and 100 mg/ml, and chlorhexidine digluconate 50 mg/ml) using the corneoxenometry (CXM) bioassay. SC was harvested from the volar forearm, the forehead and the back in 30 young adults. Each SC sample was covered by one of the neat test product or deionized water for 2 hr at 20°C. The intrinsic staining property of each antiseptic on SC was assessed by reflectance colorimetry. For the CXM bioassay, samples were then stained by a toluidine blue-basic fuschin solution in order to show protein denaturation induced by the test products. The colorimetric index of mildness (CIM = L*− Chroma C*) was measured by colorimetry. Data show that PVP-I 100 mg/ml was the least reactive antiseptic to the SC. It was significantly milder than the 2 other antiseptics. [ABSTRACT FROM AUTHOR]

Citation: IFSCC Magazine, 11 (2008) (3) 201–205 Life on earth would not be possible without skin, meaning that it must have unique properties that allow us to exist here. These properties are discussed in this short review, in particular, the physical and chemical barrier characteristics of the stratum corneum, which we now know are only possible due to the presence of water at precise and carefully controlled levels and locations. The review discusses the pivotal role water plays in both stratum corneum mechanics/integrity and stratum corneum regulation/maturation and reinforces the critical role played by cosmetic products, which moisturize and augment stratum corneum barrier function. Keywords: Skin, stratum corneum, water, barrier, confocal raman, moisturizer, corneocyte [ABSTRACT FROM AUTHOR]