Documentation of normal stratum corneum scaling in an average population: features of differences among age, ethnicity and body site

Risk factors of skin barrier dysfunction in older adults: A systematic review

AIM

Skin barrier dysfunction can trigger various skin disorders in older adults. Skin barrier assessment is essential for nurses and caregivers to prevent skin disorders; however, the evidence available for clinical assessment is limited. This systematic review aimed to clarify the risk factors of skin barrier dysfunction in older adults.

METHODS

This review adhered to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. The four databases were searched using multiple terms related to "aged" and "skin barrier." The search was initially run on April 19, 2023, and rerun on October 12, 2023. Peer-reviewed quantitative studies in English were included, with no publication time limit being set. Two reviewers assessed the risk of bias in a blinded and independent manner using JBI tools. Owing to the heterogeneity of the results, a narrative synthesis was performed.

RESULTS

Among the database-identified 4833 studies, 20 studies were included. The extracted factors were categorized as demographic characteristics, functional characteristics, chronic diseases, nutritional status, skin condition, and environmental factors. However, owing to high risk of bias and inconsistent results across studies, only chronic kidney disease and dry skin were considered risk factors for skin barrier dysfunction in older adults.

CONCLUSIONS

Assessment of chronic kidney disease and dry skin in daily skin care may guide the development of personalized skincare programs to maintain skin integrity in older adults. Furthermore, cohort studies that consider confounding factors and the reliability of measurements are needed for an in-depth investigation into skin barrier dysfunction and more risk factors.

Carbon dioxide ameliorates reduced desquamation in dry scaly skin via protease activation

OBJECTIVE

Scaling, a phenomenon showing an abnormal detachment of the stratum corneum (SC) owing to desquamation dysfunction, is commonly observed in various skin diseases or xerotic skin due to ageing and low humidity. Therefore, it is considered that ameliorating the disturbed desquamatory process of the SC leads to improvement in scaling. Carbon dioxide (CO₂ ) is known to be good for some skin diseases; however, the effect of CO₂ on scaling and its mechanism are not sufficiently clear. We aimed to elucidate the effect of transepidermal application of CO₂ on scaling and its mechanism of action.

METHODS

Twenty healthy men with mild scaling on the cheeks were recruited for a double-blind, placebo-controlled, split-face study. They applied the formulation containing CO₂ twice daily for 1 week. After the study, the SC was collected by tape stripping to analyse desquamatory protease activities and degradation of extracellular corneodesmosomes. Furthermore, the contribution of pH to proteolysis of the corneodesmosome by CO₂ was evaluated using three-dimensional (3D) cultured epidermal models.

RESULTS

The spectroscopic absorbance of tape strips, used as scaling indicators, was decreased, concomitantly with the amelioration of incomplete degradation of desmoglein-1, one of the main corneodesmosomal proteins, and activation of trypsin-like protease in the SC by transepidermal application of CO₂ . Experiments using 3D cultured epidermis showed that pH in the epidermal tissue was lowered by CO₂ , whereas a pH change was not observed with the application of the formulation containing hydrochloric acid, which was added to equalize the pH to that of the CO₂ formulation.

CONCLUSION

The transcutaneous application of CO₂ ameliorates reduced desquamatory process in xerotic skin, with concomitant mild acidification of the SC, thereby leading to improvement in scaling. Thus, CO₂ may have an advantage of efficiently and safely counteracting scaling of various skin disorders.

Facial skin mapping: from single point bio-instrumental evaluation to continuous visualization of skin hydration, barrier function, skin surface pH, and sebum in different ethnic skin types

Dry skin is one of the most important concerns of consumers worldwide. Despite huge efforts over several decades, the personal care industry still does not offer a perfect solution to satisfy the unmet needs of consumers for moisturising treatments in different ethnic groups. The paucity of data for the underlying cellular and biochemical problems in, and the effects of moisturisers on photodamaged facial skin may partly explain this. Mainly, single point measurements are used to understand the effects of products on skin physiology even on surrogate skin sites such as the non‐photodamaged volar forearm. Some groups have developed discontinuous facial maps of skin biophysical properties, however, in 2014 a continuous facial analysis of bio‐instrumental evaluations was developed using a heat map approach. These maps enabled a continuous visualization of features that not only revealed an unexpected complexity of facial skin but also indicated that use of surrogate skin sites for facial skin is inappropriate. We have demonstrated that remarkable gradients of skin hydration, TEWL, skin surface pH and sebum exist within short distances across the face and the gradients are distinctive among different ethnic groups. In addition, these studies have demonstrated that darkly‐pigmented individuals do not necessarily have a better skin barrier function than their less‐pigmented counterparts and that Caucasians have a lower facial skin surface pH compared with more pigmented subjects. Overall, there are no correlations between capacitance, TEWL and skin surface pH including individual topology angle values. Novel 3D camera approaches have also been used to facilitate a more precise assignment of measurement sites and visualisation. The 3D facial colour mappings illustrated precisely the local moisturising effects of a moisturising cream. There were subtle ethnic differences in efficacy that may be related to underlying skin biochemistry and/or ethnic differences in product application. A placebo‐controlled study using conductance measurements in Chinese subjects is also reported. Finally, a new whole face statistical approach has been taken to prove differences in skin parameters but also of moisturiser treatment that adds further to our understanding of the ethnic differences in skin physiology and product application. This paper reviews the background of the development and application of this methodology.

Reconstructed Skin Models Revealed Unexpected Differences in Epidermal African and Caucasian Skin

Clinical observations of both normal and pathological skin have shown that there is a heterogeneity based on the skin origin type. Beside external factors, intrinsic differences in skin cells could be a central element to determine skin types. This study aimed to understand the in vitro behaviour of epidermal cells of African and Caucasian skin types in the context of 3D reconstructed skin. Full-thickness skin models were constructed with site matched human keratinocytes and papillary fibroblasts to investigate potential skin type related differences. We report that reconstructed skin epidermis exhibited remarkable differences regarding stratification and differentiation according to skin types, as demonstrated by histological appearance, gene expression analysed by DNA microarray and quantitative proteomic analysis. Signalling pathways and processes related to terminal differentiation and lipid/ceramide metabolism were up-regulated in epidermis constructed with keratinocytes from Caucasian skin type when compared to that of keratinocytes from African skin type. Specifically, the expression of proteins involved in the processing of filaggrins was found different between skin models. Overall, we show unexpected differences in epidermal morphogenesis and differentiation between keratinocytes of Caucasian and African skin types in in vitro reconstructed skin containing papillary fibroblasts that could explain the differences in ethnic related skin behaviour.

Personalized skincare: from molecular basis to clinical and commercial applications

Individual responses of human skin to the environmental stress are determined by differences in the anatomy and physiology that are closely linked to the genetic characteristics such as pigmentation. Ethnic skin phenotypes can be distinguished based on defined genotypic traits, structural organization and compartmentalized sensitivity to distinct extrinsic aging factors. These differences are not only responsible for the variation in skin performance after exposure to damaging conditions, but can also affect the mechanisms of drug absorption, sensitization and other longer term effects. The unique characteristics of the individual skin function and, particularly, of the ethnic skin type are currently considered to shape the future of clinical and pharmacologic interventions as a basis for personalized skincare. Individual approaches to skincare render a novel and actively growing area with a range of biomedical and commercial applications within cosmetics industry. In this review, we summarize the aspects of the molecular and clinical manifestations of the environmental stress on human skin and proposed protective mechanisms that are linked to ethnic differences and pathophysiology of extrinsic skin aging. We subsequently discuss the possible applications and translation of this knowledge into personalized skincare.

Morphological Characteristics of Residual Skin Surface Components Collected from the Surface of Facial Skin in Women of Different Age

Background

Problems of skin aging and its prevention currently attract increasing attention with the growth of human life expectancy. The morphology of the stratum corneum (SC) is well known, but investigation of age-related changes of its structure is difficult in the absence of non-invasive sampling methods. The residual skin surface components (RSSC) that overlay the SC can be easily collected non-invasively.

Objective

The aim of this study was to examine morphology of RSSC samples collected from the surface of facial skin of healthy female volunteers of different age.

Methods

RSSC samples were non-invasively collected from 53 adult female volunteers (22 aged in the range 18∼25 years and 31 aged in the range 50∼73 years). The samples were analysed microscopically.

Results

Distinct age-related changes were determined for lipid droplet size, corneocyte desquamation level and lipid crystal count. There was a significant (p=0.0006) decrease in lipid droplet size among older women. Similarly, significantly (p=0.0401) lower lipid crystal numbers were present in the older group. Conversely, corneocyte desquamation was significantly higher (p=0.0007) in older women. No age-related difference in microbial presence in the RSSC could be detected. Result patterns were generally similar to those previously found in male volunteers; however gender-related differences in the absolute values were revealed.

Conclusion

Non-invasively collected RSSC samples allow identifying age-related changes on facial skin surface. The results of this study highlight gender-dependence of distinct elements of age-associated impairment of epidermal barrier and can be employed for developing new approaches to prevent changes associated with skin aging.

Updates in the understanding and treatments of skin & hair disorders in women of color

Skin of color comprises a diverse and expanding population of individuals. In particular, women of color represent an increasing subset of patients who frequently seek dermatologic care. Acne, melasma, and alopecia are among the most common skin disorders seen in this patient population. Understanding the differences in the basic science of skin and hair is imperative in addressing their unique needs. Despite the paucity of conclusive data on racial and ethnic differences in skin of color, certain biologic differences do exist, which affect the disease presentations of several cutaneous disorders in pigmented skin. While the overall pathogenesis and treatments for acne in women of color are similar to Caucasian men and women, individuals with darker skin types present more frequently with dyschromias from acne, which can be difficult to manage. Melasma is an acquired pigmentary disorder seen commonly in women with darker skin types and is strongly associated with ultraviolet (UV) radiation, genetic factors, and hormonal influences. Lastly, certain hair care practices and hairstyles are unique among women of African descent, which may contribute to specific types of hair loss seen in this population, such as traction alopecia, trichorrhexis nodosa and central centrifugal cicatricial alopecia (CCCA).

Water-Holding and Transport Properties of Skin Stratum Corneum of Infants and Toddlers Are Different from Those of Adults: Studies in Three Geographical Regions and Four Ethnic Groups

BACKGROUND/OBJECTIVE

Epidermal structure, function, and composition are different in white infants and adults. We investigated whether ethnicity and location contribute to differences in functional and clinical measurements of skin barrier function during the first years of life and in adults.

METHODS

Children (n = 397, ages 3-49 mos) and women (n = 117, mean age 31 yrs) were enrolled at independent centers in Beijing, China (ethnic Chinese), Skillman, New Jersey (white, African American), and Mumbai, India (ethnic South Asian). Water barrier properties of the stratum corneum were assessed using high-frequency conductance and transepidermal water loss (TEWL) on the dorsal forearm and upper inner arm. Digital imaging was used to evaluate facial erythema and scaling.

RESULTS

Despite differences in local climate, TEWL was similar in adults. In children, conductance and TEWL decreased monotonically from age 3 months to 4 years. In children from Beijing, TEWL values were higher in both arm locations than in children in Mumbai and Skillman. No significant differences were observed in TEWL or conductance between the white and African American groups.

CONCLUSION

In general, TEWL and conductance were greater on the upper inner arm than the dorsal forearm. Erythema and scaling were observed most often in subjects from Beijing and most infrequently in subjects from Mumbai. Stratum corneum water barrier properties were different in children and adults. Although there may be differences in these properties between ethnic groups in childhood, TEWL values were similar in adults across the three geographic locations and four ethnicities.

Updates in the understanding and treatments of skin & hair disorders in women of color

Skin of color comprises a diverse and expanding population of individuals. In particular, women of color represent an increasing subset of patients who frequently seek dermatologic care. Acne, melasma, and alopecia are among the most common skin disorders seen in this patient population. Understanding the differences in the basic science of skin and hair is imperative in addressing their unique needs. Despite the paucity of conclusive data on racial and ethnic differences in skin of color, certain biologic differences do exist, which affect the disease presentations of several cutaneous disorders in pigmented skin. While the overall pathogenesis and treatments for acne in women of color are similar to Caucasian men and women, individuals with darker skin types present more frequently with dyschromias from acne, which can be difficult to manage. Melasma is an acquired pigmentary disorder seen commonly in women with darker skin types and is strongly associated with ultraviolet (UV) radiation, genetic factors, and hormonal influences. Lastly, certain hair care practices and hairstyles are unique among women of African descent, which may contribute to specific types of hair loss seen in this population, such as traction alopecia, trichorrhexis nodosa and central centrifugal cicatricial alopecia (CCCA).

Genetics and skin aging

Skin aging is a complex process and underlies multiple influences with the probable involvement of heritable and various environmental factors. Several theories have been conducted regarding the pathomechanisms of aged skin, however fundamental mechanisms still remain poorly understood. This article addresses the influence of genetics on skin aging and in particular deals with the differences observed in ethnic populations and between both genders. Recent studies indicate that male and female aged skin differs as far as the type, the consistency and the sensitivity to external factors is concerned. The same has been also documented between elderly people of different origin. Consequently, the aging process taking place in both genders and in diverse ethnic groups should be examined separately and products specialized to each population should be developed in order to satisfy the special needs.