Variation of biophysical parameters of the skin with age, gender, and body region

qMAP enabled microanatomical mapping of human skin aging

Aging is a major driver of diseases in humans. Identifying features associated with aging is essential for designing robust intervention strategies and discovering novel biomarkers of aging. Extensive studies at both the molecular and organ/whole-body physiological scales have helped determined features associated with aging. However, the lack of meso-scale studies, particularly at the tissue level, limits the ability to translate findings made at molecular scale to impaired tissue functions associated with aging. In this work, we established a tissue image analysis workflow - quantitative micro-anatomical phenotyping (qMAP) - that leverages deep learning and machine vision to fully label tissue and cellular compartments in tissue sections. The fully mapped tissue images address the challenges of finding an interpretable feature set to quantitatively profile age-related microanatomic changes. We optimized qMAP for skin tissues and applied it to a cohort of 99 donors aged 14 to 92. We extracted 914 microanatomic features and found that a broad spectrum of these features, represented by 10 cores processes, are strongly associated with aging. Our analysis shows that microanatomical features of the skin can predict aging with a mean absolute error (MAE) of 7.7 years, comparable to state-of-the-art epigenetic clocks. Our study demonstrates that tissue-level architectural changes are strongly associated with aging and represent a novel category of aging biomarkers that complement molecular markers. Our results highlight the complex and underexplored multi-scale relationship between molecular and tissue microanatomic scales.

Prospective randomized double-blind comparative study of topical acetyl zingerone with tetrahexyldecyl ascorbate versus tetrahexyldecyl ascorbate alone on facial photoaging

BACKGROUND

Tetrahexydecyl ascorbate (THDA) is a lipophilic precursor to ascorbic acid that may be stabilized by acetyl zingerone (AZ). Studies have shown that the topical application of THDA may have photoprotective effects. Similarly, AZ has been shown to mitigate oxidative and inflammatory stress, thereby improving the appearance of photoaging.

AIMS

To examine the effects of THDA and AZ (THDA-AZ) on skin photoaging compared to THDA alone.

PATIENTS/METHODS

In this double-blind, randomized controlled trial, healthy individuals aged 30 to 65 were included and 44 participants were randomized to receive either THDA-AZ (THDA 5% + AZ 1%) or THDA only (THDA 5%) for 8 weeks. Facial photographs were taken at 0, 4, and 8 weeks to analyze wrinkle severity, pigment intensity, and redness intensity. A skin colorimeter was used to assess infraorbital pigmentation and erythema. Self-perception of skin and tolerability were assessed through questionnaires.

RESULTS

Average wrinkle severity was significantly decreased in the THDA-AZ group at Weeks 4 and 8 by 0.75% (p = 0.023) and 3.72% (p = 0.048), respectively, compared to the THDA group where wrinkle severity at Weeks 4 and 8 was increased by 7.88% and 4.48%, respectively. Facial pigment intensity was significantly decreased in the THDA-AZ group by 4.10% (p = 0.0002) at Week 8 compared to a 0.69% decrease in the THDA group. Facial redness intensity was decreased in the THDA-AZ group at Weeks 4 and 8 by 3.73% (p = 0.0162) and 14.25% (p = 0.045), respectively, compared to the THDA group where at Weeks 4 and 8 erythema increased by 27.5% and 8.34%, respectively. There were no significant differences in either group for infraorbital pigmentation or erythema.

CONCLUSIONS

Daily use of combined THDA and AZ may improve facial wrinkle severity, pigment intensity, and erythema to a greater extent than THDA. While THDA alone increases facial wrinkle severity and erythema, the addition of AZ reduces both.

An exploratory study of structural and microvascular changes in the skin following electrical shaving using optical coherence topography

BACKGROUND

Consumer products such as electrical shavers exert a combination of dynamic loading in the form of pressure and shear on the skin. This mechanical stimulus can lead to discomfort and skin tissue responses characterised as "Skin Sensitivity". To minimise discomfort following shaving, there is a need to establish specific stimulus-response relationships using advanced tools such as optical coherence tomography (OCT).

OBJECTIVE

To explore the spatial and temporal changes in skin morphology and microvascular function following an electrical shaving stimulus.

METHODS

Ten healthy male volunteers were recruited. The study included a 60-s electrical shaving stimulus on the forearm, cheek and neck. Skin parameters were recorded at baseline, 20 min post stimulus and 24 h post stimulus. Structural and dynamic skin parameters were estimated using OCT, while transepidermal water loss (TEWL) was recorded to provide reference values for skin barrier function.

RESULTS

At baseline, six of the eight parameters revealed statistically significant differences between the forearm and the facial sites, while only surface roughness (Rq) and reflectivity were statistically different (p < 0.05) between the cheek and neck. At 20 min post shaving, there was a significant increase in the TEWL values accompanied by increased blood perfusion, with varying magnitude of change dependent on the anatomical site. Recovery characteristics were observed 24 h post stimulus with most parameters returning to basal values, highlighting the transient influence of the stimulus.

CONCLUSIONS

OCT parameters revealed spatial and temporal differences in the skin tissue response to electrical shaving. This approach could inform shaver design and prevent skin sensitivity.

Weakened tanning ability is an important mechanism for evolutionary skin lightening in East Asians

The evolution of light-skin pigmentation among Eurasians is considered as an adaptation to the high-latitude environments. East Asians are ideal populations for studying skin color evolution because of the complex environment of East Asia. Here, we report a strong selection signal for the pigmentation gene phenylalanine hydroxylase (PAH) in light-skinned Han Chinese individuals. The intron mutation rs10778203 in PAH is enriched in East Asians and is significantly associated with skin color of the back of the hand in Han Chinese males (P < 0.05). In vitro luciferase and transcription factor binding assays show that the ancestral allele of rs10778203 could bind to SMAD2 and has a significant enhancer activity for PAH. However, the derived T allele (the major allele in East Asians) of rs10778203 decreases the binding activity of transcription factors and enhancer activity. Meanwhile, the derived T allele of rs10778203 shows a weaker ultraviolet radiation response in A375 cells and zebrafish embryos. Furthermore, rs10778203 decreases melanin production in transgenic zebrafish embryos after ultraviolet B (UVB) treatment. Collectively, PAH is a potential pigmentation gene that regulates skin tanning ability. Natural selection has enriched the adaptive allele, resulting in weakened tanning ability in East Asians, suggesting a unique genetic mechanism for evolutionary skin lightening in East Asians.

Assessment of Intraday Variations in Skin Indentation Resistance

INTRODUCTION

Information about the mechanical properties of skin and their changes with age and other conditions is important to help characterize skin physiology and pathological changes. One method to obtain this information is to measure the force required to indent the skin to a specified indentation depth (FORCE). This process measures the tissue's resistance to indentation or its compressibility and is related to the tissue's elastic modulus. Since such measurements are made in clinical and other settings at various times of day (TOD), it is useful to estimate the extent of intraday variations in FORCE that may be expected. This report focuses on this issue.

METHOD

FORCE was self-measured on the volar forearm, 5 cm distal to the antecubital fossa, every two hours from 08:00 to 24:00 hours on two consecutive days by 12 medical students (six females and six males) who were trained in the measurement process using an indentation device (SkinFibroMeter). Variability in FORCE versus TOD was analyzed using the nonparametric Friedman test and differences between genders by the nonparametric Wilcoxon test. Differences between the first day (day 1) and the second day (day 2) were tested at each TOD. The whole-body fat percentage (FAT%) and water percentage (H2O%) were determined for each participant via bioimpedance measurements at 50 KHz.

RESULTS

The age and BMI of the combined group (mean ± SD) were 24.5 ± 1.5 years and 23.2 ± 3.3 kg/m2. The overall average FORCE (mean ± SD) for the day over the 16 hours was 84.1 ± 22.7 mN and for day 2, it was 83.4 ± 28.5 mN with no significant difference between day 1 and day 2. For females, the overall two-day average FORCE (mean ± SD) over the 16 hours was 81.8 ± 20.3 mN and for males, it was 85.7 ± 30.1 mN with no significant difference between them (p = 0.271). Overall, there was no statistically significant difference in FORCE among TOD (p = 0.568). FORCE was not correlated with either FAT%, HTO%, or BMI.

CONCLUSION

The findings indicate no statistically significant variation in indentation force in females, males, or combined concerning the TOD of the measurement or differences between consecutive days at corresponding times. This suggests that whether such measurements are done in a research setting or within a clinic, they can be done at various TOD with minimal expected variation for a given subject. However, an extension of these findings to persons with skin conditions or ages not herein evaluated must await further study.

Establishment and application of perceived age prediction model for the periocular aging research of Chinese Han women

BACKGROUND

The assessment of skin aging through skin measurements faces limitations, making perceived age evaluation a more valuable and direct tool for assessing skin aging. Given that the aging process markedly affects the appearance of the eye contour, characterizing the eye region could be beneficial for perceived age assessment. This study aimed to analyze age-correlated changes in the eye contour within the Chinese Han female population and to develop, validate, and apply a multiple linear regression model for predicting perceived age.

MATERIALS AND METHODS

A naïve panel of 107 Chinese women assessed the perceived ages of 212 Chinese Han women. Instrumental analysis evaluated periorbital parameters, including palpebral fissure width (PFW), palpebral fissure height (PFH), acclivity of palpebral fissure (AX), angle of inner canthal (AEN), and angle of outer canthal (AEX). These parameters were used to construct a multiple linear regression model for predicting the perceived ages of Chinese Han women. A combined treatment using Fotona 4D and an anti-aging eye cream, formulated with plant extracts, peptides, and antioxidants, was conducted to verify the cream's anti-aging efficacy and safety. This eye cream was then tested in a large-scale clinical trial involving 101 participants. The prediction model was employed in this trial to assess the perceived ages of the women after an 8-week application of the eye cream.

RESULTS

All parameters were observed to decrease with age. An intergroup comparison indicated that eyelid aging in Chinese Han women accelerates beyond the age of 50. Consequently, a linear regression model was constructed and validated, with the perceived age being calculated as 183.159 - 1.078 * AEN - 4.487 * PFW + 6.061 * PFH - 1.003 * AX - 0.328 * AEX. The anti-aging efficacy and safety of the eye cream were confirmed through combined treatment with Fotona 4D, showing improvements in wrinkles, elasticity, and dark circles under the eyes. In a large-scale clinical evaluation using this eye cream, a perceived age prediction model was applied, suggesting that 8 weeks of use made participants appear 2.25 years younger.

CONCLUSION

Our study developed and validated a multiple linear regression model to predict the perceived age of Chinese Han women. This model was successfully utilized in a large-scale clinical evaluation of anti-aging eye cream, revealing that 8 weeks of usage made participants appear 2.25 years younger. This method effectively bridges the gap between clinical research and consumer perceptions, explores the complex factors influencing perceived age, and aims to improve anti-aging formulations.

Strategies in surface engineering for the regulation of microclimates in skin-medical product interactions

There is a growing number of personal healthcare devices that are in prolonged contact with the skin. The functionality of these products is linked to the interface formed by the contact between the medical apparatus and the skin. The interface can be characterised by its topology, compliance, and moisture and thermal regulating capabilities. Many devices are, however, described to have suboptimal and occlusive contacts, resulting in physiological unfavourable microclimates at the interface. The resulting poor management of moisture and temperature can impact the functionality and utility of the device and, in severe cases, lead to physical harm to the user. Being able to control the microclimate is therefore expected to limit medical-device related injuries and prevent associated skin complications. Surface engineering can modify and potentially enhance the regulation of the microclimate factors surrounding the interface between a product's surface and the skin. This review provides an overview of potential engineering solutions considering the needs for, and influences on, regulation of temperature and moisture by considering the skin-medical device interface as a system. These findings serve as a platform for the anticipated progress in the role of surface engineering for skin-device microclimate regulation.

Sex- and age-dependent skin mechanics-A detailed look in mice

Skin aging is of immense societal and, thus, scientific interest. Because mechanics play a critical role in skin's function, a plethora of studies have investigated age-induced changes in skin mechanics. Nonetheless, much remains to be learned about the mechanics of aging skin. This is especially true when considering sex as a biological variable. In our work, we set out to answer some of these questions using mice as a model system. Specifically, we combined mechanical testing, histology, collagen assays, and two-photon microscopy to identify age- and sex-dependent changes in skin mechanics and to relate them to structural, microstructural, and compositional factors. Our work revealed that skin stiffness, thickness, and collagen content all decreased with age and were sex dependent. Interestingly, sex differences in stiffness were age induced. We hope our findings not only further our fundamental understanding of skin aging but also highlight both age and sex as important variables when conducting studies on skin mechanics. STATEMENT OF SIGNIFICANCE: Our work addresses the question, "How do sex and age affect the mechanics of skin?" Answering this question is of both scientific and societal importance. We do so in mice as a model system. Thereby, we hope to add clarity to a body of literature that appears divided on the effect of both factors. Our findings have important implications for those studying age and sex differences, especially in mice as a model system.

Young Chinese female body skin pigmentation map: A pilot study

BACKGROUND

Most studies have discussed variations in facial skin colour based on age, gender, and anatomical site within a specific ethnic group. However, skin pigmentation on the body is also a concern for many people.

AIM

The aim of this study is to gather baseline data for Chinese young females, conduct a comprehensive assessment of body skin pigmentation, and create a body skin pigmentation map.

METHOD

Individual type angle (ITA°) was registered by CL 400 and melanin index (MI) was registered by MX 18 in 100 body points of 20 Chinese females. A total of 12,000 measurements were recorded.

RESULT

Our results showed significant differences among the symmetrical points on both sides of the body, including the clavicle, inner wrists, groin, inner ankle, elbow, armpit, waist side, the space between the thumb and index finger, instep, back shoulder, and popliteal space. Of all the points tested on the body, the points with the most severe skin pigmentation were the back of the neck, the heel, the elbow, and the popliteal space.

CONCLUSION

This is the first comprehensive study of skin pigmentation conducted on the human body. In young Chinese women, the points with the most severe skin pigmentation were the back of the neck, heels, elbows, and the popliteal space.

Correlating facial skin parameters with age and gender in population of Shaanxi Province, China

OBJECTIVE

This study was designed to comprehensively evaluate the changes in facial skin biophysical parameters with age, as well the influence of gender differences in populations of Shaanxi Province, China.

METHODS

Fourteen skin parameters, including stratum corneum hydration (SCH), transdermal water loss (TEWL), erythema, melanin, R0, R2, R5, R7, F4, gloss, skin surface pH, skin erythema index (a*), wrinkle length, and sebum, were measured by noninvasive instruments in 481 volunteers from Shaanxi Province. Spearman correlation analysis was performed to analyze the relationship between skin parameters and age. Additionally, skin parameters were analyzed for different age groups and different genders.

RESULTS

The results of the study showed a linear decrease in skin surface pH and sebum content with age, and the skin elasticity parameters R0, R2, R5, and R7 decreased significantly at the age of 54-65 years. Wrinkle length showed a linear and increase with age. R5 showed a weak negative correlation with age, R2, R7, and sebum content showed a moderate negative correlation, while wrinkle length showed a strong positive correlation. Considering the effect of gender on skin parameters, the results showed that SCH and gloss were lower in men than in women, while TEWL, erythema, melanin, wrinkle length, and sebum were higher than in women. However, there was no difference in skin elasticity between them.

CONCLUSION

The facial skin parameters, especially for the wrinkle length, exhibited the strong correlation relationship with ages in Shaanxi Province. Meanwhile, most skin parameters show significant differences with gender, which can provide a reference for future research and development in the field of cosmetics.

Effect of Lumenato a Tomato derived oral supplement on improving skin barrier strength

INTRODUCTION

Improvement of skin barrier strength could lead to healthy and youthful appearance. "Beauty inside-out" approach using nutraceuticals such as tomato derived carotenoids to support skin barrier strength could be of benefit to the ageing population.

METHOD

A panel of 60 female subjects were provided with the Lumenato capsules (containing carotenoids) or placebo capsules as nutritional supplements for 3 months. Skin health and barrier function were observed using evaporimeter which measures trans epidermal water loss (TEWL). Barrier strength was determined by study of the number of strippings required to disrupt skin barrier and barrier repair was observed in terms of TEWL a few hours after barrier disruption. Cutometer was used to observe skin firmness and elasticity. Measurements were obtained before treatment and after 4 and 12 weeks of use.

RESULTS

Results indicated a statistically significant improvement (p < 0.05) in skin barrier strength; a higher number of strippings were required to disrupt skin barrier after 12 weeks of supplement use. There was also a significant improvement in skin firmness and elasticity as observed with a cutometer.

CONCLUSION

Based on the confines and conditions of this study, oral supplementation with Lumenato resulted in significant improvement in skin barrier as well as skin firmness and elasticity.

Is Burning Mouth Syndrome Associated with Extraoral Dryness? A Systematic Review

Burning mouth syndrome (BMS) is characterized by a persistent intraoral burning sensation, often experienced by postmenopausal women. The etiology of BMS remains partially understood, and consequently, treatments remain suboptimal. Extraoral manifestations of BMS, such as extraoral dryness, are less studied. However, it has been suggested that the identification of the frequency and patterns of extraoral dryness and potential underlying mechanisms are essential to optimize treatment strategies and reduce the burden of disease. Therefore, we conducted this systematic review to provide existing evidence about extraoral dryness in BMS. The guidelines for the conduction and reporting of systematic reviews were followed. An electronic search was conducted in four major databases-PubMed, Web of Science, COCHRANE Library, and EBSCOhost-and the grey literature was assessed through Google Scholar. From each included article, information on extraoral dryness in BMS was extracted, and odds ratios were calculated for extraoral dryness among BMS patients compared with non-BMS controls. The findings demonstrated higher odds of the prevalence of extraoral dryness in BMS, which was found to a high degree in the lips, eyes, skin, and genitalia. The pattern of spread and locations of extraoral dryness propose a potential central mechanism. Based on our findings, we encourage the standardization of the assessment, recording, and reporting of the extraoral characteristics of BMS, including extraoral dryness, which can lead to better management strategies and enhance the quality of life of the affected patients.

Vertical contact forces affect vibration perception in human hairy skin

Background

Skin is the largest organ of the human body and fulfills many important functions, like detecting mechanical stimuli. Skin can be divided into glabrous (non-hairy) and hairy skin. These two skin types differ with regard to their mechanical properties and in the distribution of mechanoreceptors. Although many investigations focus on glabrous skin, hairy skin still plays a fundamental role in various activities, e.g., with regard to the perception of pleasantness or for developing wearable vibrotactile devices for pattern recognition in persons with disabilities. Unfortunately, investigations on influencing factors, like vertical contactor force, are scarce for hairy skin. Similarly, it would also be interesting to investigate whether regional vibratory sensitivity differences are present across the human torso. Hence, this study investigated the effects of vertical contactor forces and different anatomical locations on vibration perception. Four anatomical torso regions were studied. Based on findings in glabrous skin, we generally hypothesized improved vibration perception with increasing contactor forces and regional sensitivity differences between the anatomical locations.

Methods

Forty young and healthy individuals participated (23.0 ± 2.0 yrs), and vibration perception thresholds (VPTs) were determined at 30 Hz for three vertical force levels (0.6, 2.4, and 4.8 N) at four torso locations (sternum, deltoid/shoulder, lower back, middle lateral torso side).

Results

Higher contactor forces resulted in lower VPTs corresponding to improved vibration perception, regardless of anatomical location. In addition, the sternum region was more sensitive than the remaining three regions, regardless of force level. The reasons for these findings may be a varying number and activation pattern of afferents activated under the different conditions. The findings of this study complement the understanding of vibrotactile sensitivity in hairy skin and may offer implications when developing vibrotactile devices or clothing/textiles, for example.

Association of Epidermal Biophysical Properties with Obesity and Its Implications

BACKGROUND

Obesity is a condition defined by an excess amount of body fat, with body mass index (BMI) of 30 and higher. It is associated with a number of other medical conditions, including insulin resistance, diabetes mellitus, and cardiovascular diseases, as well as dyslipidemia, and it is also associated with several cutaneous disorders such as atopic dermatitis, psoriasis, intertriginous dermatitis, acanthosis nigricans and skin infections.

SUMMARY

Evidence suggests a link between obesity and epidermal dysfunction. Generally, individuals with obesity display higher transepidermal water loss rate and lower stratum corneum hydration levels, although no association of obesity with epidermal dysfunction has been documented. Results of skin surface pH are controversial. But study demonstrated a positive correlation of BMI with skin surface pH on both the forearm and the shin in males, suggesting that the changes in epidermal function vary with gender in individuals with obesity.

KEY MESSAGES

This review summarizes the association between obesity and epidermal function, and discusses possible underlying mechanisms. Individuals with obesity exhibit poor epidermal permeability barrier and lower stratum corneum hydration levels. Because of the pathogenic role of compromised epidermal function in inflammation, which is also linked to obesity, improvement in epidermal function could benefit individuals with obesity, particularly those with abnormalities in epidermal function.

Stability Profile and Clinical Evaluation of an Innovative Hydrogel Containing Polymeric Micelles as Drug Delivery Systems with Oregano Essential Oil against Fibroepithelial Polyps

Skin tags, also known as fibroepithelial polyps (FPs) or acrochordons, are soft, pigmented excrescences, with a prevalence of 50-60% in the population, occurring especially in the fourth decade of life. To date, FPs have been efficiently eliminated using minimum invasive methods such as surgical removal, cauterization, laser irradiation, and cryosurgery. Over-the-counter treatments are also of interest for patients due to their non-invasive character, but their clinical efficiency has not been clearly demonstrated. This study was designed in order to evaluate the efficacy of a modern-pharmaceutical-formulation-type poloxamer-based binary hydrogel, having Origanum vulgare L. essential oil (OEO-PbH) as an active ingredient in the management of FPs. The formulation has been shown to possess good qualities in terms of stability and sterility. Non-invasive measurements revealed changes in some physiological skin parameters. An increase in transepidermal water loss (TEWL) and erythema index was noted, while skin surface water content (SWC) decreased during eight weeks of treatment. The macroscopic evaluation revealed that the FPs dried and shrunk after topical treatment with OEO-PbH. Clinically, patients presented a lowering of the number of lesions on the treated area of 20-30% after one month of treatment and around 50% after the second month. Histopathological examination suggests that topical treatment with OEO-PbH may induce histological changes in the epidermis, dermis, and fibrovascular cores of FPs, including a loss of thickness, reduced size and number of blood vessels, and low cellularity. These changes may contribute to the observed reduction in size of FPs after treatment with OEO-PbH.

Ultraviolet light induces mechanical and structural changes in full thickness human skin

While the detrimental health effects of prolonged ultraviolet (UV) irradiation on skin health have been widely accepted, the biomechanical process by which photoaging occurs and the relative effects of irradiation with different UV ranges on skin biomechanics have remained relatively unexplored. In this study, the effects of UV-induced photoageing are explored by quantifying the changes in the mechanical properties of full-thickness human skin irradiated with UVA and UVB light for incident dosages up to 1600 J/cm2. Mechanical testing of skin samples excised parallel and perpendicular to the predominant collagen fiber orientation show a rise in the fractional relative difference of elastic modulus, fracture stress, and toughness with increased UV irradiation. These changes become significant with UVA incident dosages of 1200 J/cm2 for samples excised both parallel and perpendicular to the dominant collagen fiber orientation. However, while mechanical changes occur in samples aligned with the collagen orientation at UVB dosages of 1200 J/cm2, statistical differences in samples perpendicular to the collagen orientation emerge only for UVB dosages of 1600 J/cm2. No notable or consistent trend is observed for the fracture strain. Analyses of toughness changes with maximum absorbed dosage reveals that no one UV range is more impactful in inducing mechanical property changes, but rather these changes scale with maximum absorbed energy. Evaluation of the structural characteristics of collagen further reveals an increase in collagen fiber bundle density with UV irradiation, but not collagen tortuosity, potentially linking mechanical changes to altered microstructure.

Sex differences in the skin microbiome of burn scars

Sex differences are observed in various spectrums of skin diseases, and there are differences in wound healing rate. Herein, sex differences were identified for the newly healed skin microbiome of burn patients. Fifty-two skin samples (26 normal skin, 26 burn scars) were collected from 26 burn patients (12 male, 14 female) and microbiota analysis was performed. The correlation between skin microbiota and biomechanical properties of burn scars was also investigated. There were no significant differences in clinical characteristics between male and female patients. Considering the biomechanical properties of burn scars and normal skin around it performed before sample collection, the mean erythema level of men's normal skin was significantly higher than that of women, whereas the mean levels of melanin, transepidermal water loss and skin hydration showed no significant sex differences. The erythrocyte sedimentation rate was significantly higher in females than that in males. Alpha diversity showed no significant differences between normal skin and burn scars in the male group. However, the scar was significantly higher than that of normal skin in the female group. Microbial network analysis revealed that the male group had more complex microbial network than the female group. Additionally, in the male group, the edge density and clustering coefficient were higher in burn scars when compared to normal skin, than the female group. There were sex differences in the results of microbiome of normal skin and burn scars. Some of the altered microbiota have been correlated with the biomechanical properties of burn scars. In conclusion, sex difference in the burn scar microbiome was confirmed. These results suggest that burn treatment strategies should vary with sex.

Characteristics of current perception produced by intermediate-frequency contact currents in healthy adults

Introduction

Contact electrical currents in humans stimulate peripheral nerves at frequencies of <100 kHz, producing sensations such as tingling. At frequencies above 100 kHz, heating becomes dominant, resulting in a sensation of warmth. When the current amplitude exceeds the threshold, the sensation results in discomfort or pain. In international guidelines and standards for human protection from electromagnetic fields, the limit for the contact current amplitude has been prescribed. Although the types of sensations produced by contact current at low frequencies, i.e., approximately 50-60 Hz, and the corresponding perception thresholds have been investigated, there is a lack of knowledge about those in the intermediate-frequency band-particularly from 100 kHz to 10 MHz.

Methods

In this study, we investigated the current-perception threshold and types of sensations for 88 healthy adults (range: 20-79 years old) with a fingertip exposed to contact currents at 100 kHz, 300 kHz, 1 MHz, 3 MHz, and 10 MHz.

Results

The current perception thresholds at frequencies ranging from 300 kHz to 10 MHz were 20-30% higher than those at 100 kHz (p < 0.001). In addition, a statistical analysis revealed that the perception thresholds were correlated with the age or finger circumference: older participants and those with larger finger circumferences exhibited higher thresholds. At frequencies of ≥300 kHz, the contact current mainly produced a warmth sensation, which differed from the tingling/pricking sensation produced by the current at 100 kHz.

Discussion

These results indicate that there exists a transition of the produced sensations and their perception threshold between 100 kHz and 300 kHz. The findings of this study are useful for revising the international guidelines and standards for contact currents at intermediate frequencies.

Clinical trial registration

https://center6.umin.ac.jp/cgi-open-bin/icdr_e/ctr_view.cgi?recptno=R000045660, identifier UMIN 000045213.

Human glabrous skin contains crystallized urea dendriform structures in the stratum corneum which affect the hydration levels

Glabrous skin is hair-free skin with a high density of sweat glands, which is found on the palms, and soles of mammalians, covered with a thick stratum corneum. Dry hands are often an occupational problem which deserves attention from dermatologists. Urea is found in the skin as a component of the natural moisturizing factor and of sweat. We report the discovery of dendrimer structures of crystalized urea in the stratum corneum of palmar glabrous skin using laser scanning microscopy. The chemical and structural nature of the urea crystallites was investigated in vivo by non-invasive techniques. The relation of crystallization to skin hydration was explored. We analysed the index finger, small finger and tenar palmar area of 18 study participants using non-invasive optical methods, such as laser scanning microscopy, Raman microspectroscopy and two-photon tomography. Skin hydration was measured using corneometry. Crystalline urea structures were found in the stratum corneum of about two-thirds of the participants. Participants with a higher density of crystallized urea structures exhibited a lower skin hydration. The chemical nature and the crystalline structure of the urea were confirmed by Raman microspectroscopy and by second harmonic generated signals in two-photon tomography. The presence of urea dendrimer crystals in the glabrous skin seems to reduce the water binding capacity leading to dry hands. These findings highlight a new direction in understanding the mechanisms leading to dry hands and open opportunities for the development of better moisturizers and hand disinfection products and for diagnostic of dry skin.

Trend of changes in epidermal biophysical properties in the Chinese aged 1 month to 17-year old

BACKGROUND

Although it is known that epidermal biophysical properties vary with age and gender, the changes in epidermal biophysical properties over the time from baby to adolescence have not been elucidated yet. In the present study, we assessed the trend of changes in transepidermal water loss rates (TEWL), stratum corneum hydration, and skin surface pH in Chinese children.

PARTICIPANTS AND METHODS

A total of 780 boys and 610 girls, aged 1 month to 17-year old, were enrolled in this study. TEWL and stratum corneum hydration on the forearm and the shin were measured with GPSkin Barrier, whereas skin surface pH was measured with portable skin pH meter.

RESULTS

Overall, TEWL and stratum corneum hydration levels decreased, whereas skin surface pH increased in children from 1-month old to 17-year old. Significant decline in TEWL was observed on both the forearm and the shin of girls, and the shin of boys aged 13-17-year old. Similarly, marked decline in stratum corneum hydration levels started at ages of 6-12-year old. In contrast, decline in skin surface pH was observed in both girls and boys aged one to 12-month old except on the forearm of boys. Afterward, skin surface pH remained either stable or slight increase except on the shin of boys aged >12 months to 3-year old.

CONCLUSIONS

These results demonstrate that both TEWL and stratum corneum hydration levels decrease, whereas skin surface pH increases in children aged 1 month to 17-year old. The changes in these biophysical properties vary with age, gender, and body site.

Transepidermal water loss and stratum corneum hydration in forearm versus hand palm

BACKGROUND

Skin measurements of transepidermal water loss (TEWL) and stratum corneum hydration (SCH) reflect different aspects of skin physiology. Since epidermal water loss depends on epidermal-to-air water vapor gradients, a possible quantitative relationship between TEWL and SCH may exist. This investigation's purpose was to test the possible TEWL-SCH relationship.

MATERIALS AND METHODS

SCH and TEWL were measured noninvasively on forearm and palmer thenar eminence (hand) in 40 young adults (20 males) along with total body fat percentage (FAT) via bioimpedance.

RESULTS

A significant positive nonlinear correlation (p < 0.001) was detected between SCH and TEWL in hands of the male cohort that occurred when SCH exceeded a threshold level. This threshold level was not exceeded in male or female forearms and forearms did not display a SCH-TEWL correlation. There was a weak inverse dependence of TEWL on FAT on both forearm and hand (p < 0.05), but no SCH-FAT relationship was observed. TEWL values on the forearm and hand were moderately correlated with each other (p = 0.002) but SCH values were not.

CONCLUSION

The findings clarify the relationship between forearm and palmer hydration and TEWL values, and their relationship to total body fat percentages in young healthy adults. The significant correlation between palmer stratum corneum hydration and palmer TEWL that was discovered in the male but not the female cohort suggests a threshold hydration level for which TEWL depends both on skin barrier function and stratum corneum hydration. This implies that conditions with increased SCH may in part account for elevated TEWL values.

An evaluation of mechanical and biophysical skin parameters at different body locations

BACKGROUND

Skin is the largest organ in the body, representing an important interface to monitor health and disease. However, there is significant variation in skin properties for different ages, genders and body regions due to the differences in the structure and morphology of the skin tissues. This study aimed to evaluate the use of non-invasive tools to discriminate a range of mechanical and functional skin parameters from different skin sites.

MATERIALS AND METHODS

A cohort of 15 healthy volunteers was recruited following appropriate informed consent. Four well-established CE-marked non-invasive techniques were used to measure four anatomical regions: palm, forearm, sole and lower lumbar L3, using a repeated measures design. Skin parameters included trans-epidermal water loss (TEWL), pH (acidity), erythema, stratum corneum hydration and stiffness and elasticity using Myoton Pro (skin and muscle probe). Differences between body locations for each parameter and the intra-rater reliability between days were evaluated by the same operator.

RESULTS

The results indicate that parameters differed significantly between skin sites. For the Myoton skin probe, the sole recorded the highest stiffness value of 1006 N/m (SD ± 179), while the lower lumbar recorded the least value of 484 N/m (SD ± 160). The muscle indenter Myoton probe revealed the palm's highest value of 754 N/m (± 108), and the lower lumbar recorded the least value of 208 N/m (SD ± 44). TEWL values were lowest on the forearm, averaging 11 g/m2/h, and highest on the palm, averaging 41 g/m2/h. Similar skin hydration levels were recorded in three of the four sites, with the main difference being observed in the sole averaging 13 arbitrary units. Erythema values were characterised by a high degree of inter-subject variation, and no significant differences between sites or sides were observed. The Myoton Pro Skin showed excellent reliability (intra-class correlation coefficients > 0.70) for all sites with exception of one site right lower back; the Myoton pro muscle probes showed good to poor reliability (0.90-017), the corneometer showed excellent reliability (>0.75) among all the sites tested, and the TEWL showed Good to poor reliability (0.74-0.4) among sites.

CONCLUSION

The study revealed that using non-invasive methods, the biophysical properties of skin can be mapped, and significant differences in the mechanical and functional properties of skin were observed. These parameters were reliably recorded between days, providing a basis for their use in assessing and monitoring changes in the skin during health and disease.

Melanin levels in relation to vitamin D among first-generation immigrants from different ethnic groups and origins: A comparative national Canadian cross-sectional study

Introduction

Immigrants to Western countries tend to have darker skin than native-born populations. We examined the relationship between skin melanin and serum vitamin D (vitD) [S-25(OH)D] levels and explored whether melanin levels explained S-25(OH)D variations between immigrants and native-born Canadians. This study offers novel findings as no such study has been conducted.

Methods

We used a national cross-sectional population-based design with data from the Canadian Health Measures Survey (CHMS). Skin melanin levels among first-generation immigrants based on their ethnicity and origin/country of birth were compared with white and native-born populations. We assessed the association between S-25(OH)D and melanin after adjusting for independent variables related to S-25(OH)D, melanin level, and immigration status.

Results

Of 11,579 participants, 21.9% were immigrants aged 3-79 years (mean age 39.23 years). Compared with non-immigrants, immigrants had lower S-25(OH)D levels (mean: 51.23 vs. 62.72; 95% CI: 8.37, 14.62; P < 0.001) but higher melanin levels (mean [SE]: 17.08 [0.25] vs. 16.29 [0.29]; 95% CI: -1.29, -0.281; P = 0.004). Melanin did not differ by length of stay in Canada but was weakly positively correlated (r = 0.088, P < 0.001) with S-25(OH)D. Sex (male), age (≥18 years), summer/fall seasons, sunlight exposure, sunscreen non-use, smoking, and alcohol consumption were associated with higher melanin levels, whereas indoor tanning use was not.

Conclusion

Skin melanin levels were associated with sociodemographic and behavioral characteristics. Immigrants had higher melanin levels, but melanin did not differ by length of stay in Canada. The weak positive correlation between melanin and S-25(OH)D suggested confounding factors may impact the relationship between melanin levels, S-25(OH)D, and immigration status.

Learning from dermoscopic images in association with clinical metadata for skin lesion segmentation and classification

Automatic segmentation and classification of lesions are two clinically significant tasks in the computer-aided diagnosis of skin diseases. Both tasks are challenging due to the nonnegligible lesion differences in dermoscopic images from different patients. In this paper, we propose a novel pipeline to efficiently implement skin lesions' segmentation and classification tasks, which consists of a segmentation network and a classification network. To improve the performance of the segmentation network, we propose a novel module of Multi-Scale Holistic Feature Exploration (MSH) to thoroughly exploit perceptual clues latent among multi-scale feature maps as synthesized by the decoder. The MSH module enables holistic exploration of features across multiple scales to more effectively support downstream image analysis tasks. To boost the performance of the classification network, we propose a novel module of Cross-Modality Collaborative Feature Exploration (CMC) to discover latent discriminative features by collaboratively exploiting potential relationships between cross-modal features of dermoscopic images and clinical metadata. The CMC module enables dynamically capturing versatile interaction effects among cross-modal features during the model's representation learning procedure by discriminatively and adaptively learning the interaction weight associated with each crossmodality feature pair. In addition, to effectively reduce background noise and boost the lesion discrimination ability of the classification network, we crop the images based on lesion masks generated by the best segmentation model. We evaluate the proposed pipeline on the four public skin lesion datasets, where the ISIC 2018 and PH2 are for segmentation, and the ISIC 2019 and ISIC 2020 are combined into a new dataset, ISIC 2019&2020, for classification. It achieves a Jaccard index of 83.31% and 90.14% in skin lesion segmentation, an AUC of 97.98% and an Accuracy of 92.63% in skin lesion classification, which is superior to the performance of representative state-of-the-art skin lesion segmentation and classification methods. Last but not least, the new model for segmentation utilizes much fewer model parameters (3.3 M) than its peer approaches, leading to a greatly reduced number of labeled samples required for model training, which obtains substantially stronger robustness than its peers.

Advanced thermal sensing techniques for characterizing the physical properties of skin

Measurements of the thermal properties of the skin can serve as the basis for a noninvasive, quantitative characterization of dermatological health and physiological status. Applications range from the detection of subtle spatiotemporal changes in skin temperature associated with thermoregulatory processes, to the evaluation of depth-dependent compositional properties and hydration levels, to the assessment of various features of microvascular/macrovascular blood flow. Examples of recent advances for performing such measurements include thin, skin-interfaced systems that enable continuous, real-time monitoring of the intrinsic thermal properties of the skin beyond its superficial layers, with a path to reliable, inexpensive instruments that offer potential for widespread use as diagnostic tools in clinical settings or in the home. This paper reviews the foundational aspects of the latest thermal sensing techniques with applicability to the skin, summarizes the various devices that exploit these concepts, and provides an overview of specific areas of application in the context of skin health. A concluding section presents an outlook on the challenges and prospects for research in this field.

Textile-Based Wearable Sensor for Skin Hydration Monitoring

This research describes a wearable skin hydration sensor based on cotton textile to determine the state of hydration within the skin via impedance analysis. The sensor structure comprises a textile substrate, thermoplastic over-layer, conductive patterns, and encapsulant, designed for stable and reliable monitoring of the skin's impedance change in relation to hydration level. The porcine skin with different hydration levels was prepared as a model system of the skin, and the textile-based sensor carefully investigated the porcine skin samples' impedance characteristics. The impedance study reveals that (1) the total impedance of skin decreases as its hydration level increases, and (2) the impedance of the stratum corneum and epidermis layers are more dominantly affected by the hydration level of the skin than the dermis layer. Even after repetitive bending cycles, the impedance data of skin measured by the sensor exhibit a reliable dependence on the skin hydration level, which validates the flexibility and durability of the sensor. Finally, it is shown that the textile-based skin hydration sensor can detect various body parts' different hydration levels of human skin while maintaining a stable conformal contact with the skin. The resulting data are well-matched with the readings from a commercial skin hydration sensor.

Early Detection of Skin Disorders and Diseases Using Radiometry

Skin diseases and disorders have a significant impact on people’s health and quality of life. Current medical practice suggests different methodologies for detecting and diagnosing skin diseases and conditions. Most of these require medical tests, laboratory analyses, images, and healthcare professionals to assess the results. This consumes time, money, and effort, and the waiting time is stressful for the patient. Therefore, it is an essential requirement to develop a new automatic method for the non-invasive diagnosis of skin diseases and disorders without the need for healthcare professionals or being in a medical clinic. This research proposes millimeter-wave (MMW) radiometry as a non-contact sensor for the non-invasive diagnosis of skin diseases and conditions. Reflectance measurements performed using 90 GHz radiometry were conducted on two samples of participants; sample 1 consisted of 60 participants (30 males and 30 females) with healthy skin, and sample 2 contained 60 participants (30 males and 30 females) suffering from skin diseases and conditions, which were: basal cell carcinoma (BCC), squamous cell carcinoma (SCC), burn wounds, and eczema. Radiometric measurements show substantial differences in reflectance in the range of 0.02–0.27 between healthy and unhealthy regions of the skin on the same person. These results indicate that radiometry, as a non-contact sensor, can identify and distinguish between healthy and diseased regions of the skin. This indicates the potential of using radiometry as a non-invasive technique for the early detection of skin diseases and disorders.

Stratum corneum hydration in healthy adult humans according to the skin area, age and sex: a systematic review and meta-analysis

Stratum corneum (SC) hydration is one of the most important skin biophysical parameters, which is affected by age, sex and anatomic site. We conducted a systematic review and meta-analysis to provide detailed information on baseline values of SC hydration in healthy human adults, according to the skin area, age and sex. The databases Medline, Embase, Web of Science and Scopus were searched for primary reports, with in vivo corneometry measurements, which were conducted on disease-free skin of human subjects, aged 18+ years in English. Risk of bias was evaluated using the critical appraisal tools for JBI Systematic Reviews, and only low-risk studies were selected. The comparison was performed in each skin area between males and females and also between young- and middle-age subjects. Among 323 Retrieved titles, full texts of 259 articles were read, and 240 studies were excluded due to unclear or insufficient reporting of SC hydration, as well as high or medium risk of bias. 19 studies (including 113 records) providing data about SC hydration in 12 skin areas were included in the final data synthesis. Pooled sample sizes ranged from n = 32 for lips to a maximum of n = 3202 for cheeks. The lowest hydration of 12.5 [95% CI 11.05-13.94] was reported for the back, and the highest hydration of 64.34) [95 CI% 62.07-64.59] for the periorbital area. Facial skin showed higher water content compared with other areas. There were also site-dependent differences in the hydration level of the facial skin. Comparisons between two age groups, and male and female participants, did not show any statistically significant differences. The main limitation was we included studies using only one measurement device. The quality of reporting SC hydration in humans should be increased in future studies.

Facial Skin Aging Stages in Chinese Females

Background

Facial skin is exposed to the environment, which marks it with obvious signs of aging. Based on multi-dimensional non-invasive evaluation data, female facial skin can be characterized in detail. However, there are few studies on the general aging rules of facial skin. Most skin aging studies divide the ages into 5–10-year intervals, so they have lacked dynamic matching with facial skin aging.

Aim

To explore facial skin aging rules, discuss the main parameters of facial skin aging, propose an unequal-distance aging division method based on the main skin parameters, and study the skin characteristics of Chinese women of different aging stages.

Methods

We comprehensively described the skin status as 24 non-invasive skin parameters belonging to five dimensions: skin wrinkles, texture, stain, color and barrier function. We performed polynomial fitting on the 21 skin parameters that were significantly correlated with age and derived the rules of aging in the different dimensions. Based on the wrinkle dimension, the facial skin aging process was divided into four stages, and the skin characteristics of the different stages were compared.

Results

Skin wrinkles increased, texture deteriorated, acne decreased, pigment spots increased, skin tone darkened, and sebum secretion decreased with age, according to the polynomial fitting. The aging stage was divided into an incubation period (18–30 years old), an aging occurrence period (31–42 years old), a rapid aging period (43–47 years old), and a stable aging period (48–60 years old), according to the wrinkles. Different aging stages had different skin characteristics.

Conclusion

The incubation period is the critical period for the appearance of skin stains; the skin texture gradually deteriorates during the aging occurrence period; the rapid aging period is a critical period for the aging of skin parameters; skin status during the stable aging period is the worst.

Biochemical, structural and physical changes in aging human skin, and their relationship

Skin is the largest organ of the human body, having the purpose of regulating temperature, protecting us from microbes or mechanical shocks, and allowing the sensations from touch. It is generally accepted that aging induces profound changes in the skin's biochemical, structural and physical properties, which can lead to impaired biological functions and/or diverse diseases. So far, the effects of aging on these skin properties have been well documented. However, very few studies have focused exclusively on the relationship among these critical properties in the aging process, which is this review's primary focus. Many in vivo, ex vivo, and in vitro techniques have been previously used to characterize these properties of the skin. This review aims to provide a comprehensive overview on the effects of aging on the changes in biochemical, structural, and physical properties, and explore the potential mechanisms of skin with the relation between these properties. First, we review different or contradictory results of aging-related changes in representative parameters of each property, including the interpretations of the findings. Next, we discuss the need for a standardized method to characterize aging-related changes in these properties, to improve the way of defining age-property relationship. Moreover, potential mechanisms based on the previous results are explored by linking the biochemical, structural, and physical properties. Finally, the need to study changes of various functional properties in the separate skin layers is addressed. This review can help understand the underlying mechanism of aging-related alterations, to improve the evaluation of the aging process and guide effective treatment strategies for aging-related diseases.

Biomarkers and Detection Platforms for Human Health and Performance Monitoring: A Review

Human health and performance monitoring (HHPM) is imperative to provide information necessary for protecting, sustaining, evaluating, and improving personnel in various occupational sectors, such as industry, academy, sports, recreation, and military. While various commercially wearable sensors are on the market with their capability of "quantitative assessments" on human health, physical, and psychological states, their sensing is mostly based on physical traits, and thus lacks precision in HHPM. Minimally or noninvasive biomarkers detectable from the human body, such as body fluid (e.g., sweat, tear, urine, and interstitial fluid), exhaled breath, and skin surface, can provide abundant additional information to the HHPM. Detecting these biomarkers with novel or existing sensor technologies is emerging as critical human monitoring research. This review provides a broad perspective on the state of the art biosensor technologies for HHPM, including the list of biomarkers and their physiochemical/physical characteristics, fundamental sensing principles, and high-performance sensing transducers. Further, this paper expands to the additional scope on the key technical challenges in applying the current HHPM system to the real field.

Ultrasonic microrheology for ex vivo skin explants monitoring: A proof of concept

As an answer to alternative non-animal testing, biosensors dedicated to the ex vivo skin explants monitoring are a challenge to study physiological-like behavior and optimize new topical products. Because of the skin viscoelastic behavior, mechanical tests are commonly based on macroscopic measurement and give global descriptors of its state. Other techniques, including photoacoustic ones, are more focused on the molecular scale. There is a gap to fill in the mesoscopic range to get information about the microstructure of the skin. This article presents the proof-of-concept of a biosensor coupling a thickness shear-mode transducer with human skin explants kept in life-like state for a week. Thanks to a multifrequency analysis of the transducer impedance, this biosensor is able to monitor the viscoelastic properties of the skin. To extract the complex shear modulus and the microstructural evolutions, a mechanical model based on fractional calculus is used. As a preliminary results, the sensitivity of the sensor to probe the skin viscoelasticity in lifelike state and the impact of its culture medium are presented. A suitable microstructural coefficient is also extracted in order to identify mechanical breaches in the skin barrier after the application of peeling products.

Monitoring the Skin Biophysical Parameters Among Coronavirus Patients for Three Days in a Row: a Preliminary Study

The coronavirus epidemic 2019 is spreading all over the world now. Several parameters are used to monitor the status of hospitalized patients; however, monitoring variations in biophysical properties of the skin has not been investigated yet. In this preliminary study, we seek to monitor skin biophysical parameters among coronavirus patients for three days in a row. Skin moisture, pH, sebum, and temperature during the three days were monitored in 30 coronavirus patients by using non-invasive portable instruments. Skin biophysical parameters were increased on the third day of monitoring compared to the first one. In addition, the increase in both skin moisture and temperature were statistically significant. According to the results of this preliminary study, skin biophysical parameters changed (increased) during the specified period in which the patients were monitored. However, changes in skin sebum content and pH were not significant. These skin parameters need to be further investigated until we know their indication ability for the health condition of coronavirus patients in clinical applications.

Biophysical properties of redness-prone skin in Korean women

BACKGROUND

Facial skin redness can have a negative impact on the quality of life. In this study, we investigated the skin biophysical parameters associated with facial skin redness as a function of aging.

METHODS

Our aims were as follows: (1) to understand the impact of non-pathological facial skin redness on the quality of life of Korean women through a survey; and (2) compare skin biophysical properties between women with and without facial skin redness.

RESULTS

Women aged between 20 and 39 years perceived their own facial skin redness at a higher rate than those aged ≥40 years. In addition, in redness-prone women, the intensity of skin redness and skin surface perfusion were higher, while skin hydration was lower regardless of age. In redness-prone women aged ≥40 years, the values for transepidermal water loss, elasticity, and skin thickness were lower, and the mean pore depth was greater. Facial redness intensity was higher, and the distribution was wider in redness-prone younger women, while only redness intensity increased in the older age group.

CONCLUSIONS

Overall, redness-prone women aged ≥40 years had weaker skin properties. Our study indicated the age-related biophysical characteristics of non-pathological facial skin redness. We believe that our findings will help improve its negative effects.

Effect of gender, muscle type and skinfold thickness on myometric parameters in young people

Background

The aim of the study was to compare the mechanical properties of three human skeletal muscles: biceps brachii (BB), rectus femoris (RF), and tibialis anterior (TA) at rest measured by myoton device in males (n = 16, mean age 21.2 ± 0.6 years) and females (n = 16; 21.2 ± 0.9 years) and to investigate the influence of skin and subcutaneous tissue thickness (skinfold thickness, SFT) and gender on myometric parameters of the three skeletal muscles.

Methods

We measured the following mechanical and viscoelastic muscle properties using MyotonPRO^®: frequency (F [Hz]), decrement (D [log]), stiffness (S [N/m]), relaxation time (R [ms]) and creepability (C [De]). The values of SFT for all selected muscles were assessed by caliper. A mixed-design analysis of variance with gender as between subject comparison was used for assessing the differences between gender and muscles in SFT and each of the myometric parameters separately (F, D, S, R and C). Pearson correlation coefficient or Spearman’s rank correlation coefficient between SFT and myometric parameters was conducted for males, females and males and females together. The level of statistical significance was set at α ≤ 0.05 with Bonferroni correction for multiple comparisons.

Results

The SFT over the RF, TA, and BB muscles in women was statistically significantly larger compared with that of males. In females and males, the SFT over the RF was larger than over the TA and BB, and the SFT over the TA was larger compared with over the BB. The values of F and S recorded for the TA muscle were the highest among the three muscles, while D, C, and R were lowest in TA but highest in the RF muscle in men and women. The values of F and S were smaller in females than in males. Gender comparison of D, C, and R values showed that only D for the RF was significantly lower in females than in males, and C for the RF and TA was significantly larger in females than in males. Some correlation between SFT and myometric parameters were different between males and females. For example, there was a significant, negative correlation between SFT and F for all muscles in females, and a significant, positive correlation between these parameters for BB and TA (not for RF) in males. For pooled data (males and females together), a negative significant correlation between SFT and F was observed for RF and TA (not significant for BB muscle).

Discussion

It is concluded that the TA compared with the BB and RF has significantly greater F and S but the smallest D and C and the shortest R. Gender and muscle differences in the SFT may affect the measurements of muscle properties using MyotonPRO^®. The relationship between SFT and myometric parameters is different in males and females in the RF, TA, and BB muscles. Therefore, the myometric data should be analyzed in males and females separately.

Transdermal Drug Delivery in the Pig Skin

Transdermal delivery can be accomplished through various mechanisms including formulation optimization, epidermal stratum corneum barrier disruption, or directly by removing the stratum corneum layer. Microneedling, electroporation, a combination of both and also the intradermal injection known as mesotherapy have proved efficacy in epidermal-barrier disruption. Here we analyzed the effects of these methods of epidermal-barrier disruption in the structure of the skin and the absorption of four compounds with different characteristics and properties (ketoprofen, biotin, caffein, and procaine). Swine skin (Pietrain x Durox) was used as a human analogue, both having similar structure and pharmacological release. They were biopsied at different intervals, up to 2 weeks after application. High-pressure liquid chromatography and brightfield microscopy were performed, conducting a biometric analysis and measuring histological structure and vascular status. The performed experiments led to different results in the function of the studied molecules: ketoprofen and biotin had the best concentrations with intradermal injections, while delivery methods for obtaining procaine and caffein maximum concentrations changed on the basis of the lapsed time. The studied techniques did not produce significant histological alterations after their application, except for an observed increase in Langerhans cells and melanocytes after applying electroporation, and an epidermal thinning after using microneedles, with variable results regarding dermal thickness. Although all the studied barrier disruptors can accomplish transdermal delivery, the best disruptor is dependent on the particular molecule.

Taxonomic profiling of skin microbiome and correlation with clinical skin parameters in healthy Koreans

The interest in skin microbiome differences by ethnicity, age, and gender is increasing. Compared to other ethnic groups, studies on the skin microbiome of Koreans remains insufficient; we investigated facial skin microbiome characteristics according to gender and age among Koreans. Fifty-one healthy participants were recruited, the facial skin characteristics of each donor were investigated, their skin bacterial DNA was isolated and metagenomic analysis was performed. The donors were divided into two groups for age and sex each to analyze their skin microbiomes. Moreover, we investigated the correlation between the skin microbiome and clinical characteristics. The alpha diversity of the skin microbiome was significantly higher in the elderly, and beta diversity was significantly different according to age. The comparative skin microbials showed that the genus Lawsonella was more abundant in the younger age group, and Enhydrobacter was predominant in the older age group. Staphylococcus and Corynebacterium were more abundant in males, while Lactobacillus was more abundant in females. Lawsonella had a negative correlation with skin moisture and brown spots. Staphylococcus and Corynebacterium both had negative correlations with the number of UV spots and positive correlations with transepidermal water loss (TEWL). Furthermore, Staphylococcus aureus had a negative correlation with skin moisture parameters.

Differences between perceived age and chronological age in women: A multi-ethnic and multi-centre study

Objective

Accuracy in assessing age from facial cues is important in social perception given reports of strong negative correlations between perceived age and assessments of health and attractiveness. In a multi‐ethnic and multi‐centre study, we previously documented similar patterns of female facial age assessments across ethnicities, influenced by gender and ethnicity of assessors.

Methods

Here we extend these findings by examining differences between estimated age from digital portraits and chronological age (Δ age) for 180 women from three age groups (20–34, 35–49, 50–66 years) and five ethnicities (36 images of each ethnicity, assessed for age on a continuous scale by 120 female and male raters of each ethnicity).

Results

Across ethnicities, Δ age was smallest in French assessors and largest in South African assessors. Numerically, French women were judged oldest and Chinese women youngest relative to chronological age. In younger women, Δ age was larger than in middle‐aged and older women. This effect was particularly evident when considering the interaction of women's age with assessor gender and ethnicity, independently and together, on Δ age.

Conclusion

Collectively, our findings suggest that accuracy in assessments of female age from digital portraits depends on the chronological age and ethnicity of the photographed women and the ethnicity and gender of the assessor. We discuss the findings concerning ethnic variation in skin pigmentation and visible signs of ageing and comment on implications for cosmetic science.

Influence of quarantine mask use on skin characteristics: One of the changes in our life caused by the COVID-19 pandemic

BACKGROUND

The influence of various environmental factors on skin properties is well known. However, there is a lack of research into the effect of quarantine masks on skin properties, even though the use of masks has significantly increased after the COVID-19 outbreak. Therefore, this study aimed to investigate the influence of mask use on skin properties.

MATERIALS AND METHODS

Twenty subjects were enrolled in this study. The subjects used approved quarantine masks for 6 hours a day for 2 weeks. We measured eight skin biophysical parameters: temperature, redness, pore volume, texture, elasticity, trans-epidermal water loss (TEWL), sebum content, and pH, and evaluated acne lesions before and after using quarantine masks. The evaluation was performed on the mask-wearing area of the face.

RESULTS

Skin temperature, redness, and TEWL increased significantly after a 6-hour mask use, while the sebum content increased marginally. Skin elasticity was reduced by the use of masks over 1 and 2 weeks, whereas the pore volume and the number of acne lesions increased after a 2-week mask use. The skin changes caused by mask use showed sex-based differences in the skin elasticity (after 6 hours), redness, and roughness (after 2 weeks).

CONCLUSIONS

The use of quarantine masks causes a change in the skin temperature, redness, and TEWL in the short term and in skin elasticity, pores, and acne in the long term. This study revealed that prolonged mask use could have negative effects on the skin.

The examination of biophysical parameters of the skin in Polish Konik horses

This study aimed to assess the biophysical parameters of the skin in Polish Konik horses (Polish primitive horses). According to the authors, this is the first assessment performed on such a wide scale in this group of animals. The evaluation carried out is innovative both with regards to the breed of the animals and the wide scope of the physicochemical skin assessment. The study group comprised mares, stallions and geldings, and the evaluations concerned transepidermal water loss, corneometry, pH, skin temperature assessment and mexametry. These parameters were assessed in five skin regions: the lips, the right ear, the prosternum, the right side of the neck and the chest. The measurements were taken after spreading the hair apart, with the use of a Multiprobe Adapter System (MPA^®) and dedicated probes (Courage + Khazaka electronic GmbH, Cologne, Germany). The measurements revealed statistically significant differences in the values of transepidermal water loss in the lips in mares compared with stallions (P = 0.023) and also in stallions compared with geldings (P = 0.009). Corneometry showed significantly higher results in the neck region in mares compared with stallions (P = 0.037) and the prosternum areas in mares and geldings compared with stallions (P = 0.037 and P = 0.018). Skin pH measurement on the right side of the neck rendered significantly higher values in stallions than in mares (P = 0.037). In geldings, the skin temperature was significantly higher than in stallions (P = 0.049). Once the appropriate physicochemical values for specific animal species and breeds are determined, non-invasive methods of skin examination in many diseases and also methods of evaluation of the efficacy and/or adverse effects of applied medications can be established.

Biophysical and ultrasonographic changes in pityriasis rosea compared with uninvolved skin

BACKGROUND

Pityriasis rosea (PR) is a common, self-limited, inflammatory papulosquamous skin disease with a possible viral etiology.

OBJECTIVE

The goal of this study was to evaluate skin biophysical properties in patients with PR compared with uninvolved skin to better understand the pathogenesis of PR.

METHODS

Stratum corneum hydration, transepidermal water loss, surface friction, pH, sebum, melanin, erythema, temperature, elasticity parameters (R0, R2, R5), thickness, and echodensity of the epidermis and dermis were measured on lesions of classic PR in 21 patients and compared with control sites (average of uninvolved perilesional and symmetrical skin) with a paired t test.

RESULTS

Stratum corneum hydration (p < .001), R0 (p = .003), R2 (p = .001), R5 (p = .003), and echodensity of the dermis (p = .006) were significantly lower, whereas transepidermal water loss (p = .001), pH (p < .001), and erythema (p < .001) were significantly higher in PR lesions. There was no significant difference in friction index, sebum, melanin content, temperature, thickness of the epidermis and dermis, and echodensity of the epidermis between PR and normal skin.

CONCLUSION

PR skin is characterized by certain alterations in biophysical properties, which are mostly correlated with histologic changes. These changes may be helpful in early, noninvasive diagnosis of PR.

THz Sensing of Human Skin: A Review of Skin Modeling Approaches

The non-ionizing and non-invasive nature of THz radiation, combined with its high sensitivity to water, has made THz imaging and spectroscopy highly attractive for in vivo biomedical applications for many years. Among them, the skin is primarily investigated due to the short penetration depth of THz waves caused by the high attenuation by water in biological samples. However, a complete model of skin describing the THz-skin interaction is still needed. This is also fundamental to reveal the optical properties of the skin from the measured THz spectrum. It is crucial that the correct model is used, not just to ensure compatibility between different works, but more importantly to ensure the reliability of the data and conclusions. Therefore, in this review, we summarize the models applied to skin used in the THz regime, and we compare their adaptability, accuracy, and limitations. We show that most of the models attempt to extract the hydration profile inside the skin while there is also the anisotropic model that displays skin structural changes in the stratum corneum.

The impact of time, environmental conditions, and sex on the degradation of bloody fingerprints on a glass surface

Dactyloscopy is the branch of forensics that deals with identifying individuals by analyzing the configurations of the friction ridges on the fingertips. The persistence and degradation of fingerprints depends on such factors as the individual's sex and BMI (body mass index) and the duration and conditions of their preservation. There is a great deal of information on how the passage of time affects the image of fingerprints composed of sebum and sweat, but little knowledge concerning the preservation of bloody fingerprints. The aim of the study was to determine the effect of sex, the state of the blood forming the print (dry vs. fresh), environmental factors (room vs. outdoor conditions), and time on the width of friction ridge impressions in fingerprints. Fingerprints made with fresh blood were found to persist longest, while prints left by women and exposed to outdoor conditions degraded most rapidly. The ambient temperature also had a significant effect on the width of friction ridge impressions and their degradation.

Measurement of Shear Wave Speed and Normalized Elastic Modulus of Human Skin with and without Dermal Striae Using Shear Wave Elastography

Supersonic shear imaging is a non-invasive technique used for detecting physiologic and pathologic changes in biological tissues. In this study, supersonic shear imaging was used to measure and compare shear wave speed (c_s) and normalized elastic modulus (E_N) values of skin with and skin without dermal striae (DS) in vivo. The values were measured at angles of 0°, 45°, 90° and 315° to the skin tension lines. In the presence of DS, a statistically significant reduction in the elasticity dermis was observed (p value <0.05). The mean values of c_s and E_N for STLs were higher in normal skin at 45° (4.26 ± 1.05 m/s and 56.23 ± 25.31 kPa) and 90° (4.26 ± 0.55 m/s and 54.91 ± 14.22 kPa), and those for DS were also higher at 45° (3.59 ± 0.72 m/s and 42.71 ± 27.97 kPa) and 90° (3.52 ± 0.65 m/s and 42.34 ± 31.68 kPa) than at other angles. Supersonic shear imaging was found to be a promising technique in the study of skin with DS. The data obtained in this study are expected to be relevant for future studies using shear wave elastography for the aforementioned purpose.

Unbearable transepidermal water loss (TEWL) experimental variability: why?

Despite the wide breadth of research, much disparity exists in transepidermal water loss (TEWL) research data-possibly due to uncontrolled experimental variables. We determined whether such experimental variables significantly impact TEWL studies and cause this disparity. An initial literature search regarding TEWL was performed to determine potential confounding variables. A subsequent search procured relevant and representative studies investigating the impact of these variables on TEWL. Variables, such as age, anatomic site, and temperature, impact TEWL and should be controlled for in TEWL studies. Other variables, such as smoking and menstrual cycle, have inconclusive results or do not provide sufficient data breadth to make a conclusion regarding its effect, if such an effect exists, on TEWL metrics. Therefore, these variables require further research to determine their potential impact on TEWL. Matching for as many experimental variables as possible may reduce the disparity in TEWL data/conclusions.

Occupational contact dermatitis in a gender perspective: North East Italian data 1996-2016

BACKGROUND

Occupational contact dermatitis (OCD) ranks high among occupational diseases in Europe, but little is known as regards OCD and jobs in a gender perspective.

OBJECTIVES

To evaluate sex prevalence of OCD according to occupational sectors and agents involved. 27381 patients (1996-2016) with suspected irritant/allergic contact dermatitis (ICD-ACD) were evaluated in North-Eastern Italy. Each patient underwent: a standardized questionnaire, a dermatologist/occupational physician evaluation and a patch test.

RESULTS

Females were younger at diagnosis (35.2 ± 11.6 years vs 37.7 ± 12.6 in males, p< 0.001) and had a lower ICD prevalence (OR 0.58, C.I. 95% 0.51 - 0.66, p < 0.001). Job categories most involved differed between sexes, with highest rank for healthcare professionals in females and machinery mechanics and filters for males. In females ACD percentage was higher in all job categories.

CONCLUSIONS

OCD characteristics differ between sexes, according to intrinsic and extrinsic factors. Use of personal care products, housekeeping products and outdoor work activities may account for different sensitization profiles.

Statistical analysis of age-related skin parameters

BACKGROUND

Due to the increasing interest in human anti-aging, demand for a higher quality of life, and technological advancement, the development of anti-aging skincare has great market prospects. Most cosmetic companies develop products driven by the market or focus on the mechanism of action of substances and the behavior of skin; however, little research utilizes skin parameters and large data methodology to develop skincare products.

OBJECTIVE

To instruct consumers to purchase skincare products and to guide skincare research toward the development of customer-targeted products.

METHODS

A total of 815 Chinese subjects (83 male; 732 female) from five different cities were included. We measured 14 indices in each subject, including moisture, transepidermal water loss (TEWL), and sebum levels. We performed multiple regression analysis to understand the relationship between skin indices and aging; a novel approach is shown using the R software.

RESULTS

The exact age at which changes in each skin index occurred could be demonstrated by this method of analysis: 39, 38, 48, 46, and 56 years old with respect to the L value, Melanin, Rt, Rm, and Rz, respectively.

CONCLUSION

With the use of statistical analysis, consumers can be more efficiently targeted and choose suitable products considering particular skin parameter changing points; thus, skincare companies will not only meet customer requirements but also better control budgets.

The Interaction of Age and Anatomical Region Influenced Skin Biophysical Characteristics of Chinese Women

BACKGROUND

Ageing is an inevitable physiology process of humans, and skin biophysical parameters change owing to genetic and environmental factors in different ethnic populations.

AIM

To gain comprehensive data on the skin biophysical parameters of different anatomical regions and to explore the change trend of the skin characteristics associated with age for the indicated regions by generalized additive model.

METHODS

We measured various skin biophysical parameters on forehead, cheek, chin and inner forearm of 178 Chinese women aged between 20 and 64 years living in Beijing. These parameters comprised skin hydration, transepidermal water loss (TEWL), sebum content, erythema index (EI), melanin index (MI), L*a*b* values, individual typology angle (ITA) and pH, which were quantified by non-invasive instruments.

RESULTS

Comparing the skin parameters among the four test areas, we observed that the hydration, TEWL, EI and a* values were significantly higher for the face than for the forearm, but the L* and ITA values were just the opposite. The cheek was the lightest and brightest region with lowest sebum content, while the chin was much darker and the forehead was yellowish. Considering the change of the skin parameters with age, TEWL, sebum content and melanin and erythema indices had a linear relationship with age, whereas skin hydration, L, a, b, ITA and pH values exhibited a non-monotonic relationship. The turning points of these curves appeared almost at the thirties, showing the lightest and evenest skin color and more hydration, with lower pH values.

CONCLUSION

This study indicates that the skin biophysical characteristics of Chinese women were significantly affected by age and body regions.