Skin Barrier Integrity Research Articles

The Origin, Intricate Nature, and Role of the Skin Surface pH (pHSS) in Barrier Integrity, Eczema, and Psoriasis

The inherent acidic nature of the stratum corneum (SC), the so-called “acid mantle”, has a multitude of effects on skin barrier integrity owing to its (patho)physiological role in skin homeostasis, antimicrobial defense, and inflammation. Several salient SC acidifying mechanisms, including the breakdown of FLG (filaggrin) protein, lipid processing, and the activity of the sodium proton pump SLC9A1/NHE1, are indispensable for the structural and functional integrity and cohesion of the SC as they contribute immensely to the origin, generation, maintenance, and overall SC acidification of the skin surface pH (pHss). As many endogenous and exogenous factors can affect the pHss, the pHss can inevitably deviate from its optimum. The elevation of the pHss is often accompanied by abnormalities in SC lipid metabolism and organization, SC cohesion, and SC integrity and is commonly observed in eczema, which is associated with symptoms of dry skin, inflammation, pruritus, and infection. In psoriasis, it seems that the pHss is altered as well; however, in this case, it is likely to be lower than the physiological pHss. Due to the negative effects of an altered pHss in both eczema and psoriasis, it has been suggested to maintain the pHss at physiological levels by utilizing pH-balanced topical cleansers and moisturizers that can improve the skin’s structural and functional integrity by benefiting skin moisturization and the regeneration and organization of the SC barrier. The principal aim of this review is to gather an understanding of the existing research and to stimulate critical thinking and inspire innovative ideas about ‘known unknowns’, considering the origin, intricate nature, and prime role of the pHss in human skin health, as well as the pathogenesis of eczema and psoriasis.

Skin Barrier Function in Neonates and Infants.

This review focuses on the skin barrier function in neonates and infants, emphasizing the structural and functional differences compared to adult skin. Neonatal and infant skin is thinner, more permeable, and less developed, which makes it more vulnerable to irritants, infections, and dehydration. Additionally, the critical role of skin pH in maintaining barrier function is discussed, noting significant changes in pH levels during early life. This review also examines the relationship between the onset of atopic dermatitis and skin barrier function, underscoring the importance of maintaining skin barrier integrity from birth to reduce the risk of atopic diseases. Finally, recommendations are offered for skincare practices in neonates and infants, emphasizing the use of mild, fragrance-free products and the importance of tailoring skincare regimens to meet the specific needs of each neonate or infant.

Assessment of Skin Condition and Efficacy of Liquid and Cream Hand Sanitizers

Hand sanitizer has become a popular alternative to traditional hand washing due to its ease of use, convenience, and effectiveness. Most hand sanitizers on the market are formulated with high concentrations of alcohol and lack of moisturizing agents, which can cause skin problems by altering the skin barrier's integrity and function with repeated use. To counteract these drying and irritating effects, a moisturizing hand sanitizer cream was developed. This study aims to assess the moisturizing efficacy of the developed cream and compare skin condition and antimicrobial effectiveness after using two different forms of hand sanitizer. The in vivo study involved comparing skin conditions after two weeks of using the developed moisturizing hand sanitizer cream and a commercial hand sanitizer liquid. Biophysical parameters such as trans epidermal water loss (TEWL), skin hydration, and elasticity were measured. Fifteen volunteers completed the study. Results showed a significant decrease in TEWL for the hand sanitizer liquid, but a gradual decrease for the cream. Skin hydration significantly decreased with the liquid but increased with the cream. Additionally, skin elasticity significantly improved with the cream compared to the liquid. Microbiological analysis indicated some contamination, but the hand sanitizer cream generally was more effective in reducing bacterial and fungal counts compared to the liquid sanitizer. In conclusion, these findings suggest that the moisturizing hand sanitizer cream not only supports skin health but also provides effective antimicrobial protection, highlighting its potential as a beneficial alternative to traditional hand sanitizers.

Cathelicidins: Opportunities and Challenges in Skin Therapeutics and Clinical Translation.

Cathelicidins are a group of cationic, amphipathic peptides that play a vital role in the innate immune response of many vertebrates, including humans. Produced by immune and epithelial cells, they serve as natural defenses against a wide range of pathogens, including bacteria, viruses, and fungi. In humans, the cathelicidin LL-37 is essential for wound healing, maintaining skin barrier integrity, and combating infections. Cathelicidins of different origins have shown potential in treating various skin conditions, including melanoma, acne, and diabetic foot ulcers. Despite their promising therapeutic potential, cathelicidins face significant challenges in clinical application. Many peptide-based therapies have failed in clinical trials due to unclear efficacy and safety concerns. Additionally, the emergence of bacterial resistance, which contradicts initial claims of non-resistance, further complicates their development. To successfully translate cathelicidins into effective clinical treatments, therefore, several obstacles must be addressed, including a better understanding of their mechanisms of action, sustainable large-scale production, optimized formulations for drug delivery and stability, and strategies to overcome microbial resistance. This review examines the current knowledge of cathelicidins and their therapeutic applications and discusses the challenges that hinder their clinical use and must be overcome to fully exploit their potential in medicine.

Natural Products as Modulators of Aryl Hydrocarbon Receptor Signaling in Atopic Dermatitis Management.

Atopic dermatitis (AD) is a chronic inflammatory skin condition characterized by immune dysregulation, skin barrier dysfunction, and a significant patient burden. Recent studies have highlighted the aryl hydrocarbon receptor (AhR) as a promising therapeutic target for AD management because of its pivotal role in modulating immune responses and maintaining skin barrier integrity. The dysfunction of the AhR pathway has been linked to AD pathogenesis, emphasizing the need for therapies that can restore its regulatory functions. Natural products have emerged as potential modulators of the AhR and are effective and safe alternatives to conventional treatments. Compounds such as curcumin, resveratrol, quercetin, and microbial metabolites have demonstrated the ability to activate AhR, reduce inflammation, and promote skin barrier function. These natural agents have fewer side effects and enhance patient compliance compared with conventional therapies, making them attractive candidates for long-term AD management. The integration of natural products targeting the AhR pathway provides a multifaceted approach that alleviates symptoms, addresses underlying disease mechanisms, and promotes sustainable improvements in skin health. This review highlights the therapeutic potential of natural AhR modulators and their potential roles in enhancing patient outcomes through novel integrative treatment strategies.

Advances of the exposome at individual levels and prevention in atopic dermatitis.

Atopic dermatitis (AD), or eczema, is an inflammatory skin disease related to environmental factors. As a heterogeneous disease, it presents with complex phenotypes and endotypes. A variety of intrinsic and extrinsic factors can promote the development of AD. While there has been extensive discussion on environmental exposure at the population and community levels, discourse on exposome at individual levels in AD remains insufficient. For example, allergens, microorganisms, parasites, dietary factors, and psychological factors such as stress and anxiety play important roles in AD development. Microorganisms, in particular, exhibit altered composition and diversity on the skin of AD patients, influencing skin barrier integrity and immune responses. The impact of certain microorganisms, such as fungi and viruses, on AD has garnered increasing attention because of their important role in maintaining skin homeostasis. Dietary factors, including sugar intake and histamine-rich foods, may modulate AD risk and severity, although findings are controversial. Allergens, particularly house dust mite allergens, and aeroallergens, exacerbate AD symptoms by promoting inflammation and barrier dysfunction. Since AD is often the first step in the atopic march, its primary prevention measures are crucial. Some preventive measures involving microorganisms, diet, and moisturizers remain controversial. Effective preventive strategies necessitate a clear understanding of the complex mechanisms of AD, especially host-microbe-environment interactions. This review summarizes recent advances in understanding various risk and protective factors, as well as primary prevention measures for AD.

Systematic characterization of the barrier function of diverse ex vivo models of damaged human skin

BackgroundThe skin barrier plays a crucial role in protecting our body against external agents. Disruption of this barrier’s function leads to increased susceptibility to infections and dermatological diseases. Damaged skin can be due to the use of detergents, sunburn or excessive scratching. In the context of the COVID-19 pandemic the recommended hygiene measures to prevent the spread of SARS-CoV-2, such as wearing masks, frequent handwashing, and the use of sanitizers, can also potentially alter the skin barrier.ObjectivesThe purpose of the study was to characterize the barrier function of ex vivo models of damaged human skin.MethodsSkin barrier damage was induced through different chemical and mechanical treatments, representative of the potential factors damaging human skin. The skin barrier function was evaluated in terms of permeability, dermal absorption capacity, stratum corneum thickness and gene expression of barrier markers. As inflammation is linked to skin barrier integrity, inflammatory markers were also analyzed.Results and discussionThe different treatments applied to ex vivo skin models allow the simulation of diverse degrees of skin damage, making these models valuable for assessing the efficacy of topical products targeted at skin repair and for studying the effects of compromised skin barrier on viral penetration.

Effects of milk powder fortified with red ginseng extracts on the skin barrier function and immunity of middle-aged women

This study investigated the effects of a nutritional milk composition containing red ginseng extract (MCCRG) on the skin barrier function and immunity of middle-aged women. Fifty women (aged, 25 to 45) consumed MCCRG orally for 56 days. Evaluations of skin phenotype, facial bacterial microbiome, immune system function, and clinical diagnoses were conducted. The results indicated that MCCRG significantly improved skin hydration, firmness, elasticity, and glossiness. Furthermore, MCCRG also reduced TEWL and wrinkles and enhanced skin barrier integrity. Additionally, high IgG levels and improved CD4+/CD8+ ratios due to MCCRG consumption increased facial microbiota diversity and immune function. Clinical diagnoses provided supplementary evidence for the efficacy of MCCRG. The findings of this study demonstrated that MCCRG, through nutritional support, enhanced both skin barrier and immune system functions. This study offers substantial evidence of the innovative therapeutic effects of nutritional support on skin barrier damage and immune function.

Regulation of keratinocyte barrier function and inflammatory response by the EGFR-STAT3 Pathway: Potential therapeutic implications of osimertinib and afatinib

The epidermal growth factor receptor (EGFR) signaling pathway is crucial for skin barrier integrity and immune response. This study explores the impact of EGFR inhibitors, osimertinib and afatinib, on keratinocyte function, focusing on keratin (KRT1, KRT17) and tight junction protein (CLDN1, CLDN2, CLDN4) expression in HaCaT cells. Osimertinib significantly increased the mRNA and protein levels of keratins and inflammatory markers, IL-6 and TNF-α, via activation of the EGFR-STAT3 signaling pathway. Co-treatment with recombinant human EGF reversed these changes, suggesting the pathway’s modulatory role. These findings underscore the potential therapeutic applications of targeting the EGFR-STAT3 axis in skin barrier dysfunction and inflammatory skin disorders.

One Acne™: A holistic management approach to improve overall skin quality and treatment outcomes in acne with or without sensitive skin

AbstractAcne and sensitive skin can take a profound toll on patients' well‐being, which can be exacerbated if the conditions are experienced together. This narrative review aims to identify appropriate treatments to facilitate a holistic management approach to acne (One Acne™), sensitive skin, and acne‐induced sequelae and describe the role of treatments in improving skin quality. Topical retinoids are considered the preferred first‐line option for acne treatment by dermatologists, either as monotherapy or in combination with other treatments, because of their ability to target various aspects of the disease. Tretinoin, trifarotene, adapalene, and tazarotene have all been assessed in clinical studies for managing acne‐associated scarring, with varying success, with the latter three reported to improve skin quality. Moreover, some corrective procedures, e.g., injectable non‐animal stabilized hyaluronic acid (NASHA) fillers, have proven effective for treating acne scarring. Both treatment types may complement each other to provide optimal treatment outcomes and patient satisfaction, as observed in several patients receiving concomitant treatment with NASHA fillers/topical trifarotene. Adjunctive use of cleansers, moisturizers, and photoprotection‐containing ingredients such as vitamin B3, glycerin, or pro‐vitamin B3 may also complement drug/corrective treatments to reduce skin irritation and risk of scarring, as well as improve skin hydration, tone, and overall appearance. This narrative review highlights that comprehensive skincare regimens should be used throughout acne patients' journeys to reduce treatment‐related irritation, improve treatment outcomes, adherence, and satisfaction, and enhance overall skin quality. Patients with sensitive skin should choose tailored skincare products to maintain skin barrier integrity and restore skin function.

Impact of Chronic Moderate Psychological Stress on Skin Aging: Exploratory Clinical Study and Cellular Functioning.

Skin is continuously exposed to environmental external and internal factors, including psychological stress (PS). PS has been reported to trigger different dermatoses such as psoriasis, atopic dermatitis, vitiligo, alopecia areata, and acne through the release of cortisol and epinephrine. To clinically explore PS-induced measurable skin aging signs in subjects with moderate versus mild chronic PS, and to investigate the effect of chronic PS on DNA damage at cellular level. In vitro stress tests with cortisol and epinephrine, and with cortisol only on extracellular matrix (ECM) synthesis, as well as on normal human skin fibroblast and keratinocyte functioning, including skin barrier and wound healing were performed. Moderately stressed subjects in the context of the clinical study had a significantly decreased antioxidant potential and impacted skin barrier integrity, as well as significantly increased signs of microrelief alterations (skin texture and fine lines) reaching an increased severity of about 32.9%. At a cellular level, DNA integrity, ECM synthesis, wound healing, and skin barrier parameters were impacted by increased stress hormone levels. The clinical exploratory studies presented herewith, as well as the study of cell functioning under stress, have provided evidence that chronic PS significantly affects skin homeostasis and triggers skin aging.

Recombinant filaggrin-2 improves skin barrier function and attenuates ultraviolet B (UVB) irradiation-induced epidermal barrier disruption

The integrity of the skin barrier is essential for maintaining skin health, with the stratum corneum and filaggrin 2 (FLG-2) playing a key role. FLG-2 deficiency or mutation has been linked to diseases such as atopic dermatitis, while external stressors such as ultraviolet B (UVB) radiation further damage the epidermal barrier. This study investigated the effects of recombinant filaggrin (rFLG) on skin barrier function and UVB induced epidermal destruction. Cell experiments showed that 10 μg/mL of rFLG could increase the mobility of HaCaT cells from 20 % to 42 %, increase the epithelial resistance (TEER) value by about 2 times, and up-regulate the tight junction associated protein by about 2 times. In mouse models of UVB-induced epidermal barrier destruction, rFLG at concentrations of 0.5, 1, and 2 mg/mL showed effective cell uptake and skin penetration, alleviating erythema, and reducing skin thickness in mice by 1.5–3 times. Among them, 2 mg/mL of rFLG treatment restored the expression of tight junction proteins (LOR, ZO-1, and caspase-14), reduced collagen degradation, and reduced oxidative stress by normalizing serum hydroxyproline and superoxide dismutase levels. In addition, 2 mg/mL of rFLG inhibited UVB-induced upregulation of matrix metalloproteinases (MMP-3 and MMP-9) and reduced pro-inflammatory factors (IL-10, IL-1α, IL-6, and TNF-α) and apoptotic markers (P38, Bax, and Bcl-2) to normal levels. These findings suggested that rFLG effectively enhanced skin barrier integrity and mitigated UVB-induced epidermal barrier destruction, highlighting its potential as a therapeutic agent for diseases associated with skin barrier dysfunction.

Mapping the relationship between atopic dermatitis and gut microbiota: a bibliometric analysis, 2014-2023.

Atopic dermatitis (AD) is a chronic inflammatory skin condition affecting a significant portion of the population, with prevalence rates of 25% in children and 7-10% in adults. AD not only poses physical challenges but also profoundly impacts patients' mental well-being and quality of life. The stability of gut microbiota is crucial for overall health and can influence AD progression by modulating immune function, skin barrier integrity, and neuroendocrine signaling, which may be an effective target for the prevention and treatment of AD. Thus, exploring the interactions between AD and gut microbiota, particularly in infants, can provide insights into potential preventive and therapeutic strategies. This study aimed to explore the correlation between AD and gut microbiota while providing an overview of current research trends and emerging areas of interest in this field. A comprehensive search was conducted on the Web of Science Core Collection (WOSCC) for relevant publications from January 1, 2014, to December 31, 2023. English-language articles and reviews were included. Two investigators independently screened the publications, and visual analysis was performed using CiteSpace, VOSviewer, Scimago Graphica, and Microsoft Excel software. A total of 804 articles were included, showing a significant increase in publications over the past decade. The United States, Wageningen University, and University Ulsan (represented by Hong SJ) had the highest number of published papers. Nutrients was the journal with the most publications, while the Journal of Allergy and Clinical Immunology had the highest number of citations and centrality among co-cited journals. Keyword visualization analysis identified "atopic dermatitis" and "gut microbiota" as central themes. Notably, there has been a notable shift in research focus over the years, with early studies concentrating on "Fecal microbiota," "caesarean section," and "first 6 months," while recent studies have highlighted the roles of "cells," "dysbiosis," and "prebiotics." This shift indicates growing interest in the underlying mechanisms and potential therapeutic interventions related to the intestinal microecology in AD treatment. The field of AD and gut microbiota research has evolved significantly, with an increasing focus on understanding the intricate interactions between gut microbiota and AD pathogenesis. Recent years have witnessed increased interest in understanding the relationship between AD and gut microbiota, with researchers conducting extensive studies exploring various aspects of this connection. This review analyzes research trends over the past decade, highlighting trends and hotspots in the study of AD, particularly in infants, and the role of microbiota. This review serves as a valuable reference for future investigations, aiming to provide deeper insights into this burgeoning field and suggests directions for future research.

Challenges in Adult Acne and the Role of Skin Care in Managing the Condition.

Acne vulgaris is a complex, multifactorial, inflammatory skin condition. Although frequently presented at dermatology clinics, the literature on adult acne is scarce, particularly concerning skin barrier function and management. We aimed to provide insights into the role of skin barrier integrity in adult acne patients and the role of cleansers and moisturizers as adjunctive to treating and maintaining adult acne.   Methods: A panel of eight dermatologists who treat adult patients with acne developed a consensus paper on the role of skin barrier function and skin care in adult acne management. The modified Delphi method comprised a face-to-face meeting and online follow-up to discuss the results of a scoping literature review. Drawing from their experience and opinions, they agreed on seven consensus statements.   Results: Epidermal barrier dysfunction plays a vital role in acne pathogenesis and asymmetrically impacts adult female acne. Erythema, pruritus, peeling, and xerosis are common adverse effects of first-line acne treatment options and, if not appropriately counseled and managed, can exacerbate, leading to regimen nonadherence and poor patient experience and outcomes. Improving patient knowledge of comprehensive acne treatments, including quality adjunctive cleansers and moisturizers, may maximize regimen efficacy and provide patients with personalized and successful acne treatment and maintenance tools. J Drugs Dermatol. 2024;23(8):674-679.     doi:10.36849/JDD.8471.

Staphylococcus aureus Proteases: Orchestrators of Skin Inflammation.

Skin homeostasis relies on a delicate balance between host proteases and protease inhibitors along with those secreted from microbial communities, as disruption to this harmony contributes to the pathogenesis of inflammatory skin disorders, including atopic dermatitis and Netherton's syndrome. In addition to being a prominent cause of skin and soft tissue infections, the gram-positive bacterium Staphylococcus aureus is a key player in inflammatory skin conditions due to its array of 10 secreted proteases. Herein we review how S. aureus proteases augment the development of inflammation in skin disorders. These mechanisms include degradation of skin barrier integrity, immune dysregulation and pruritis, and impairment of host defenses. Delineating the diverse roles of S. aureus proteases has the potential to reveal novel therapeutic strategies, such as inhibitors of proteases or their cognate target, as well as neutralizing vaccines to alleviate the burden of inflammatory skin disorders in patients.

The skin barrier and microbiome in infantile atopic dermatitis development: can skincare prevent onset?

Atopic dermatitis (AD), a prevalent Th2-dominant skin disease, involves complex genetic and environmental factors, including mutations in the Filaggrin gene and dysbiosis of skin microbiota characterized by an increased abundance of Staphylococcus aureus. Our recent findings emphasize the pivotal role of the skin barrier's integrity and microbial composition in infantile AD and allergic diseases. Early skin dysbiosis predisposes infants to AD, suggesting targeted skincare practices as a preventive strategy. The effects of skincare interventions, particularly the application of moisturizers with the appropriate molar concentration of ceramides, cholesterol, and fatty acids, play a crucial role in restoring the skin barrier. Notably, our study revealed that appropriate skincare can reduce Streptococcus abundance while supporting Cutibacterium acnes presence, thus directly linking skincare practices to microbial modulation in neonatal skin. Despite the mixed outcomes of previous Randomized Controlled Trials on the efficacy of moisturizers in AD prevention, our research points to the potential of skincare intervention as a primary preventive method against AD by minimizing the impact of genetic and environmental factors. Furthermore, our research supports the notion that early aggressive management of eczema may reduce the incidence of food allergies, highlighting the necessity for multifaceted prevention strategies that address both the skin barrier and immune sensitization. By focusing on repairing the skin barrier and adjusting the skin's microbiome from birth, we propose a novel perspective on preventing infantile AD and allergic diseases, opening new avenues for future studies, and practices in allergy prevention.

Mucormycosis: A sweet enemy, case series

Mucormycosis is a rare fungal infection caused by fungi of the Mucorales order that occurs in immunocompromised individuals or with loss of skin or mucosa barrier integrity. This report presents four cases of rhinocerebral mucormycosis attended at a third-level hospital in Cali (Colombia) during a period of three years. All patients had different case histories and times of evolution. All four had a previous or de novo diagnosis of type 2 diabetes mellitus, with glycated hemoglobin higher than 10% on admission. We ruled out other possible pathologies that could explain their immunocompromised condition. Mucormycosis diagnosis was made with direct visualization of hyaline coenocytic hyphae on biopsies. The basis of treatment was liposomal amphotericin B and surgical debridement. Two patients presented bacterial coinfection. One asked for voluntary discharge without having completed the treatment, and another one died. The remaining two have attended controls and had an adequate evolution.

P05 The aryl hydrocarbon receptor pathway is dysfunctional in atopic dermatitis

Abstract Introduction and aims Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by epidermal barrier disruption and type-2 immune dysregulation. While treatment has improved with targeted biologics, clinical response varies, highlighting the need for additional therapeutic strategies. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor and environmental sensor, which maintains skin barrier integrity and homeostasis by reducing inflammation. Upon activation, AHR induces the expression of CYP1A1, a biomarker of pathway activation and critical for AHR ligand metabolism. Tapinarof, a topical AHR agonist, is approved for psoriasis and is effective in phase III clinical trials in AD, highlighting the importance of this pathway in inflammatory skin disease. Nevertheless, AHR expression is increased in AD skin, leading to the hypothesis that the pathway is dysregulated, thus not exerting its anti-inflammatory effect. Methods Here we begin to perform a global investigation of the AHR pathway in AD. We measured AHR and CYP1A1 mRNA expression by quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) in healthy and AD skin, with spatial mRNA expression assessed by RNAscope. We also investigated AHR mRNA expression in interleukin (IL)-4 stimulated (100 ng mL−1) normal human epidermal keratinocytes (NHEKs) using qRT-PCR. Results We found that AHR mRNA is significantly upregulated in lesional AD (n = 6) compared with healthy skin (n = 9; P < 0.05), whereas CYP1A1 mRNA expression shows a downward trend in lesional AD compared with healthy skin (P = 0.063). The AHR expression pattern differs in lesional AD (n = 7) compared with healthy skin (n = 8), with AHR localizing in the epidermal basal layer. Finally, IL-4 significantly upregulated AHR mRNA (n = 4 wells; P < 0.001) expression in NHEKs compared with unstimulated cells. Conclusions Overall, our data have uncovered a dysfunctional AHR pathway in AD, with increased AHR expression, possibly driven by the AD inflammatory milieu, but reduced pathway activation. Further investigations are required to fully dissect this pathway and maximize its potential as a therapeutic target for AD.

Does sensitive skin lie in epidermal barrier impairment or abnormalities? Results from an observational study assessing biophysical parameters.

The pathophysiology of sensitive skin is largely unknown and no univocal data on the role of the epidermal barrier impairment have been identified. The aim of this study was to assess whether subjects with or without sensitive skin differ for some biophysical skin parameters, which reflect skin barrier integrity or skin hyperactivity. This observational, cross-sectional study included adult volunteers not affected with chronic inflammatory skin diseases who attended the Unit of Dermatology and the Center of Cosmetology of the University of Ferrara, Ferrara, Italy, between March 2021 and November 2022. All subjects, subdivided into those with or without sensitive skin, based on either Lactic Acid Stinging Test (LAST) result or a questionnaire-based skin sensitivity score ≥4, were tested for transepidermal water loss (TEWL), skin elasticity and hydrations and dermographism. One hundred and eighty-seven subjects were included. No significant differences in terms of TEWL, elasticity and hydration levels were recorded between subjects with sensitive skin and those without, subdivided according to both the LAST result and the questionnaire score. Dermographism was elicited more in subjects with sensitive skin than in the others, although without statistical significance. The study failed to find significant biophysical differences between sensitive and non-sensitive skin. Therefore, the role of skin barrier impairment does not appear to be a necessary condition in determining an abnormal skin sensitivity to potentially unpleasant and irritating stimuli. These findings indirectly support the relevance of a peripheral sensory neural hyperactivity in the pathophysiology of sensitive skin.

Comparative whole genome analysis of face-derived Streptococcus infantis CX-4 unravels the functions related to skin barrier.

The skin microbiome is essential in guarding against harmful pathogens and responding to environmental changes by generating substances useful in the cosmetic and pharmaceutical industries. Among these microorganisms, Streptococcus is a bacterial species identified in various isolation sources. In 2021, a strain of Streptococcus infantis, CX-4, was identified from facial skin and found to be linked to skin structure and elasticity. As the skin-derived strain differs from other S. infantis strains, which are usually of oral origin, it emphasizes the significance of bacterial variation by the environment. This study aims to explore the unique characteristics of the CX-4 compared to seven oral-derived Streptococcus strains based on the Whole-Genome Sequencing data, focusing on its potential role in skin health and its possible application in cosmetic strategies. The genome of the CX-4 strain was constructed using PacBio Sequencing, with the assembly performed using the SMRT protocol. Comparative whole-genome analysis was then performed with seven closely related strains, utilizing web-based tools like PATRIC, OrthoVenn3, and EggNOG-mapper, for various analyses, including protein association analysis using STRING. Our analysis unveiled a substantial number of Clusters of Orthologous Groups in diverse functional categories in CX-4, among which sphingosine kinase (SphK) emerged as a unique product, exclusively present in the CX-4 strain. SphK is a critical enzyme in the sphingolipid metabolic pathway, generating sphingosine-1-phosphate. The study also brought potential associations with isoprene formation and retinoic acid synthesis, the latter being a metabolite of vitamin A, renowned for its crucial function in promoting skin cell growth, differentiation, and maintaining of skin barrier integrity. These findings collectively suggest the potential of the CX-4 strain in enhancing of skin barrier functionality. Our research underscores the potential of the skin-derived S. infantis CX-4 strain by revealing unique bacterial compounds and their potential roles on human skin.