The cornified envelope: a model of cell death in the skin

The live attenuated varicella-zoster virus vaccine vOka: Molecular and cellular biology of its skin attenuation

Infection with varicella-zoster virus (VZV) causes chickenpox and shingles, both manifesting as a blistering skin rash. The skin is central to VZV, as the site of viral replication, transmission from cell-free virus in blisters and as the gateway to sensory nerves for establishing latency. The existing chickenpox vaccine is based on the live attenuated vOka strain and is impaired for replication in skin. While the genetics of the vOka vaccine have been extensively studied, critical gaps exist in understanding the molecular and cellular mechanisms of vOka attenuation, particularly in human skin models. This review aims to explore the molecular biology of vOka vaccine, focusing on its genetic diversity, interaction with host skin pathways, and the impact of vOka mutations in key VZV genes on attenuation mechanisms in human skin models. Insights from this review may guide the development of next-generation varicella vaccines and enhance the understanding of VZV pathogenesis.

Potential activity of chicken amniotic fluid in epidermal development by promoting keratinocyte differentiation

Epidermal barrier formation during fetal development, a fundamental biological process in mammals and birds, occurs in the amniotic cavity filled with amniotic fluid (AF). In keratinocytes, indispensable proteins for barrier formation are produced during differentiation, including transglutaminase 1 (TG1) and structural proteins encoded by a gene cluster, epidermal differentiation complex. In general, the chicken fetus rapidly forms a robust epidermal barrier during a relatively short embryonic day (ED); however, little is known about how chicken AF (cAF) contributes to the controls of gene expression of the factors involved in epidermal development. Here, we first demonstrated that the cross-linking activity of TG1 gradually increased, followed by the development of barrier function until ED18 in the chicken fetal epidermis. Then, we revealed that cAF harvested at specific fetal stages had the ability to enhance the expression and activity of TG1, and to facilitate the expression of genes for the other epidermal transglutaminases, structural proteins, and differentiation-related transcription factors in human cultured keratinocytes. Furthermore, the thermal denaturation of cAF components reduced cAF efficacy in promoting the expression of those factors. The fractionated proteinaceous solution of cAF possessed the activity to induce the protein expression of barrier formation-related factors, such as the transcription factor zinc finger protein 750. These results indicated that proteinaceous molecules in cAF have the potential to activate the gene expression networks involved in epidermal barrier formation. This finding will provide novel insights into the physiological role of AF in fetal epidermal development.

Nanoparticle Skin Penetration: Depths and Routes Modeled In-Silico

Nanoparticles (NPs) are increasingly explored for targeted skin penetration, particularly for pharmaceutical and cosmetic applications. However, the complex system between NP properties, skin structure, and experimental conditions poses significant challenges in predicting their penetration depth and pathways. To what depth do NPs penetrate the skin, and which pathways do they follow? These are the questions which we tried to answer in this paper. A n in-silico human skin model based on 20 years of literature on NPs skin penetration is developed. The model incorporates 19 independent parameters, including a wide range of NP properties, skin across species, and test conditions. Using random forest analysis coupled with Kennard-Stone sorting, the model achieves a high predictive accuracy of 95%. The study identifies hair follicle diameter as the most critical factor influencing NP penetration across skin layers, surpassing other skin properties, NP properties, or experimental variables. Pig and rabbit skin are the most suitable models for simulating human skin in NP penetration studies. Additionally, the in-silico model reveals that NPs in emulsions and oil-based media predominantly follow the intercellular and transappendageal route. In contrast, those embedded in aqueous media favor the intracellular route. These findings offer insights for optimizing NP-based drug delivery systems.

Relationship between time-dependent epidermal ceramide composition changes and skin barrier function in adult mice

Ceramides, especially acylceramides and protein-bound ceramides, are important for skin barrier formation. However, due to the neonatal lethality of knockout (KO) of the genes involved in the production of these ceramides, the effects of their KO in adult mice have been unclear. To investigate these effects, we created mice with tamoxifen-inducible conditional KO of the fatty acid elongase Elovl1. Following tamoxifen administration, acylceramide levels began to decrease from day 5. On day 10, impaired formation of lipid lamellae and thickening of the epidermis were observed. On day 15, protein-bound ceramide levels were substantially reduced and transepidermal water loss was increased. Changes in quantities of ceramides other than acylceramides and protein-bound ceramides and shortening of their fatty acid moieties were also observed, but time courses differed among ceramide classes. RNA sequencing revealed changes in the expression levels of genes involved in ceramide metabolism and keratinocyte proliferation and differentiation in Elovl1 conditional-KO mice. In summary, this study reveals that acylceramides and protein-bound ceramides are important for maintaining the skin barrier in adults, although they are not essential for survival. We also observed compensatory responses toward reduced skin barrier function, such as changes in gene expression, epidermal morphology, and ceramide composition.

Therapeutic Effects of Sigesbeckia pubescens Makino Against Atopic Dermatitis-Like Skin Inflammation Through the JAK2/STAT Signaling Pathway

Atopic dermatitis (AD), a chronic inflammatory skin condition, is a common allergic disorder. The human skin, the largest organ, serves as the first barrier in protecting the body against various external threats. Human epidermal keratinocytes (HEKs) in the epidermal layer and human dermal fibroblasts (HDFs) in the dermis of the skin are implicated in AD-associated skin inflammation through the secretion of diverse inflammatory mediators, including chemokines. Sigesbeckia pubescens Makino (SP), a traditional Korean and Chinese herbal remedy, is used for treating inflammatory conditions. While several pharmacological effects of SP extract (SPE) have been documented, its specific inhibitory effect on AD-related skin inflammation remains unexplored. Hence, oral administration of SPE to NC/Nga mice reduced the severity of house dust mite extract-induced dermatitis, accompanied by lowered levels of serum inflammatory mediators, decreased epidermal thickness, reduced mast cell infiltration, and restoration of skin barrier function within skin lesions. In conclusion, SPE has demonstrated the ability to alleviate skin inflammation and protect the skin barrier and shows potential as a therapeutic option for AD. SPE inhibited proinflammatory chemokine production by modulating the Janus kinase (JAK) 2/signal transducer and activator of transcription proteins (STAT) 1/STAT3 signaling pathway in IFN-γ- and TNF-α-stimulated skin cells.

MCPIP3 orchestrates the balance of epidermal proliferation and differentiation

BACKGROUND

Monocyte chemoattractant protein-induced protein 3 (MCPIP3), also called Regnase-3 and encoded by the ZC3H12C gene, is a member of the MCPIP family of RNases. Previous studies showed that MCPIP1 in keratinocytes plays a pivotal role in the maintenance of skin integrity and immunological function. Given that the expression of MCPIP3, similar to that of MCPIP1, is increased in psoriatic lesions compared with uninvolved skin, a role of MCPIP3 in the regulation of keratinocyte and epidermal biology was hypothesized.

METHODS

This study aimed to investigate the specific function of the MCPIP3 protein in the skin. The expression pattern of MCPIP3 was studied in normal human epidermal keratinocytes (NHEKs) subjected to in vitro differentiation and upon stimulation with proinflammatory factors. Mice with keratinocyte-specific deletion of MCPIP3 (Mcpip3loxP/loxPKrt14Cre; MCPIP3EKO) were generated and characterized. The response of the skin of MCPIP3EKO mice to imiquimod (IMQ) and 12-O-tetradecanoylphorbol-13-acetate (TPA) was investigated. The expression levels of key modulators of keratinocyte proliferation and differentiation were measured in MCPIP3EKO model mice and in NHEKs transiently transfected with MCPIP3-specific siRNA. Reporter assays were used to identify direct targets of MCPIP3 nucleolytic activity.

RESULTS

In human keratinocytes, the expression of ZC3H12C/MCPIP3 was rapidly induced by stimulation with TPA, IL-17a, IL-36α, and TNF-α. Although mice with keratinocyte-specific deletion of MCPIP3 (MCPIP3EKO) did not develop skin inflammation, they displayed abnormalities in skin morphology. Stimulation with IMQ and TPA exacerbated epidermal hyperplasia caused by keratinocyte-specific deficiency of MCPIP3 and led to abnormal epidermal differentiation. The expression levels of keratinocyte proliferation and differentiation markers, such as keratin-14, cyclin B1, involucrin, and the S100 calcium-binding proteins S100A7/A9, were increased in NHEKs in which MCPIP3 expression was silenced. MCPIP3 negatively regulates the level of cyclin B1 mRNA via direct nucleolytic cleavage within its 3' untranslated region.

CONCLUSIONS

The MCPIP3 protein modulates the balance of keratinocyte proliferation and differentiation and functions as a regulator of epidermal morphology in vivo.

Expression of an epidermal growth factor-transdermal peptide fusion protein in Arabidopsis thaliana and its therapeutic effects on skin barrier repair

Epidermal growth factor (EGF) is recognized for its role in regulating keratinocyte proliferation and differentiation, thereby facilitating the restoration of impaired skin barriers. Nevertheless, challenges related to the penetration and safety of EGF remain to be resolved. In this study, we evaluated the efficacy of TDP1, a transdermal peptide, in enhancing the penetration of EGF through murine skin, utilizing EGF expressed in A. thaliana. The coding sequences of the TDP1 and EGF genes were cloned as a fusion construct into a plant expression vector. The resulting plasmid, pGM3301-TDP1-EGF, was introduced into A. thaliana via the floral dip method. Positive clones were identified using polymerase chain reaction (PCR). High-expression strains were selected through Western-blot analysis and enzyme-linked immunosorbent assay (ELISA). Homozygotes plants were obtained through self-pollination. The impact of the TDP1-EGF fusion protein on the restoration of a compromised epidermal barrier was assessed using dermatoscopy. Keratinocyte (KC) proliferation was examined via hematoxylin and eosin (H&E) staining, while KC differentiation, lipid synthesis, and inflammatory factors were analyzed using reverse transcription quantitative PCR (RT-qPCR) and immunohistochemistry. Compared to other expression systems, the A. thaliana system utilized for TDP1-EGF expression offers the advantages of being devoid of toxicity from endogenous plant substances, rendering it both safe and suitable for scalable production of the recombinant protein. The yield of the TDP1-EGF fusion protein expressed in A. thaliana accounted for 0.0166% of the total soluble protein. EGF conjugated with TDP1 displayed enhanced transdermal activity compared to unconjugated EGF, as evidenced by the Franz diffusion cell assay. Furthermore, the biological efficacy of the TDP1-EGF fusion protein surpassed that of EGF alone in ameliorating epidermal barrier damage in a murine skin injury model. This research has the potential to revolutionize the development and delivery of skincare products and establishes a foundation for the application of molecular farming in skin health.

Regulation of keratinocyte proliferation and differentiation by secoiridoid oleacein in monoculture and fibroblast co-culture models

Aberrant differentiation of keratinocytes is closely associated with both pathological skin disorders and non-pathological skin conditions, making the maintenance of normal differentiation process essential for skin integrity and homeostasis. This study investigated the effect of olive-derived secoiridoid oleacein (OC) on keratinocyte proliferation and differentiation in vitro and further validated it in a co-culture model with fibroblasts mimicking a skin-like environment. OC was compared with oleuropein (OP) as a reference compound having similar chemical structure and reported effects on skin barrier formation and wound healing. Notably, OC significantly increased the proliferation makers KRT5 and KRT14 and demonstrated wound healing effect under low-calcium condition, reflecting characteristics of the basal layer. Under high-calcium condition, OC markedly upregulated differentiation markers KRT10, IVL, FLG, and TGM1, along with differentiation characteristics such as cytoplasmic extensions and cell adhesion. Transcriptomic analysis revealed that OP and OC shared a common upstream pathway, Integrin/E-cadherin-Rho-MAPK, at the cytoplasm, while they showed distinct regulatory mechanisms within the nucleus. OP induced differentiation by suppressing stemness genes through epigenetic regulation, whereas OC secured differentiation stability by suppressing proliferative gene ESR1 and activating the DNA damage response from DNA damage or mechanical stress occurring during differentiation. Our study is the first to elucidate the dual regulatory effects of OC on keratinocyte proliferation and differentiation stage-dependently as well as its underlying molecular mechanisms, suggesting that the divergent regulatory mechanisms may be due to their structural differences. These findings highlight OC as a skin protective agent for maintaining skin health and suggest its therapeutic potential for skin disorders related to abnormal differentiation.

Barrier Integrity and Immunity: Exploring the Cutaneous Front Line in Health and Disease

Immune responses are influenced by not only immune cells but also the tissue microenvironment where these cells reside. Recent advancements in understanding the underlying molecular mechanisms and structures of the epidermal tight junctions (TJs) and stratum corneum (SC) have significantly enhanced our knowledge of skin barrier functions. TJs, located in the granular layer of the epidermis, are crucial boundary elements in the differentiation process, particularly in the transition from living cells to dead cells. The SC forms from dead keratinocytes via corneoptosis and features three distinct pH zones critical for barrier function and homeostasis. Additionally, the SC-skin microbiota interactions are crucial for modulating immune responses and protecting against pathogens. In this review, we explore how these components contribute both to healthy and disease states. By targeting the skin barrier in therapeutic strategies, we can enhance its integrity, modulate immune responses, and ultimately improve outcomes for patients with inflammatory skin conditions.

The Beneficial Effects of a N-(1-Carbamoyl-2-phenyl-ethyl) Butyramide on Human Keratinocytes

Background: The skin microbiota-derived metabolite butyrate plays a pivotal role in maintaining skin health. Unfortunately, unpleasant sensorial properties and unfavorable physicochemical properties strongly limit the butyrate use in dermatology clinical practice. This study investigates the effects of N-(1-carbamoyl-2-phenyl-ethyl) butyramide (FBA), a butyric acid releaser with neutral sensorial properties on skin keratinocyte function. Methods: Immortalized human keratinocyte cell line (HaCaT cells) was treated with FBA at various concentrations (0.001-1 mM) and time points (6-48 h). Cellular proliferation was assessed using MTT assays, while barrier integrity was evaluated by measuring tight junction proteins (occludin and ZO-1). Oxidative stress was analyzed using ROS assays and Western blot for Nrf2 and NF-κB expression. Markers of differentiation and extracellular matrix proteins were measured via quantitative PCR and wound-healing capability was assessed using a scratch assay. Results: FBA significantly enhanced keratinocyte proliferation at an optimal concentration of 0.1 mM. Tight junction protein expression increased, indicating improved barrier function. FBA reduced oxidative stress by upregulating Nrf2 and suppressing NF-κB activity. It also promoted the expression of differentiation markers (e.g., keratin-1, filaggrin) and extracellular matrix proteins (e.g., collagen type I and elastin). Furthermore, FBA accelerated wound closure, demonstrating its efficacy in enhancing the mechanisms of skin repair. Conclusions: Our results demonstrate that FBA enhances human keratinocyte cell differentiation, proliferation, and skin repair while protecting against oxidative stress. Its potential in cosmetics lies in delivering butyric acid benefits without organoleptic limitations, with possible applications in several skin condition characterized by deficient butyrate production and inflammation, such as atopic dermatitis.

Safety Profile of Solanum tuberosum-Derived Exosomes: Evidence from In Vitro Experiments and Human Skin Tests

Background/Objectives: Potato (Solanum tuberosum)-derived exosomes (SDEs) are extracellular vesicles (66 nm in diameter) with therapeutic potential. SDEs suppress matrix metallopeptidases (MMPs) 1, 2, and 9, tumor necrosis factor (TNF), and interleukin 6 (IL6), while exhibiting radical-scavenging activity against the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) in vitro and mitigating hydrogen peroxide (H2O2)-induced oxidative stress in HaCaT cells. SDEs upregulate the antioxidant gene glutathione S-transferase alpha 4 (GSTA4), prevent UVB damage, and regenerate photodamaged HaCaT cells. This study evaluates SDEs' safety and skin-enhancing properties to improve their beauty-related and medical applications. Methods: The SDEs purified via ultracentrifugation were tested for their cytotoxic effects on HaCaT cell viability in scratch wound healing assays and for skin barrier gene modulation in HaCaT keratinocytes and Detroit 551 fibroblasts. A reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze the changes in skin barrier gene expression following the SDE treatment. Cosmetic prototypes containing SDEs were assessed for skin irritation, cooling effects, periorbital wrinkle reduction, elasticity, and whitening properties. Results: The cytotoxicity and human topical tests confirmed the safety of SDE application. The SDEs accelerated wound closure, elevated the skin barrier gene expression level, and improved the clinical parameters, including wrinkle reduction, elasticity enhancement, and whitening. No irritation or side effects were observed. Conclusions: This study identified natural, edible potato-derived exosomes (SDEs) as highly safe agents that significantly enhance wound healing and promote skin barrier-related gene expression. Their multifunctional anti-aging efficacy-reducing wrinkles, enhancing elasticity, and promoting whitening without irritation-positions them as promising candidates for cosmetic and dermatological innovations. These findings warrant further exploration of SDEs for therapeutic applications, including inflammatory skin disorders and drug delivery systems.

The Neovaginal Microbiota, Symptoms, and Local Immune Correlates in Transfeminine Individuals with Penile Inversion Vaginoplasty

Transfeminine people (assigned male at birth) often undergo penile inversion vaginoplasty to create vulva, a clitoris and a vaginal canal (referred to as a neovagina). After vaginoplasty, transfeminine people frequently experience gynecological concerns but their etiology is unknown due to a lack of knowledge of the neovaginal microenvironment. We characterized neovaginal microbiota and cytokines in 47 transfeminine participants. Participants self-reported sexual behaviors and symptoms, enabling correlation with bacterial (16S rRNA) and immune profiles. Four distinct clusters of co-occurring bacteria with unique immune profiles were identified. One cluster, which included Fastidiosipila , Ezakiella , and Murdochiella , was abundant, stable, and correlated with lower cytokines. Conversely, another cluster containing Howardella , Parvimonas , Fusobacterium , and Lawsonella was linked to higher cytokines. Although Lactobacillus was detected, Lactobacillus -dominance was rare. These findings underscore the need for evidence-based clinical guidelines tailored to transfeminine gynecologic care, emphasizing the vital role of the neovaginal microbiome in symptom management and sexual health.

Salivary Proteome Is Altered in Children With Small Area Thermal Burns

Saliva is a child appropriate biofluid, but it has not previously been used to evaluate the systemic response to burn injury in children. The aim of this study was to investigate the salivary proteome of children with small area thermal skin burns relative to different burn characteristics (mechanism, time to re-epithelialization and risk of emotional distress). SWATH Mass Spectrometry was used to quantify the abundance of 742 proteins in the saliva of children with burns (n = 22) and healthy controls (n = 37). Eight proteins were differentially abundant in the saliva of children with burns compared to healthy children, and these were associated with immune processes, epidermal cell differentiation and transferrin receptor binding. Eleven proteins were differentially abundant in patients with burns of different mechanisms. Scald burns had an over-representation of immune/inflammatory response processes, and contact burns had an over-representation of cornification, intermediate filament assembly and cell death cellular processes. Four proteins were elevated in patients who were at high risk for emotional distress and 15 proteins were correlated with time to wound re-epithelialization. This pilot study proves that saliva can be used for paediatric biomarker discovery and can be used as a diagnostic and prognostic sample to investigate systemic changes in a paediatric burn cohort.

zDHHC-Mediated S-Palmitoylation in Skin Health and Its Targeting as a Treatment Perspective

S-acylation, which includes S-palmitoylation, is the only known reversible lipid-based post-translational protein modification. S-palmitoylation is mediated by palmitoyl acyltransferases (PATs), a family of 23 enzymes commonly referred to as zDHHCs, which catalyze the addition of palmitate to cysteine residues on specific target proteins. Aberrant S-palmitoylation events have been linked to the pathogenesis of multiple human diseases. While there have been advances in elucidating the molecular mechanisms underlying the pathogenesis of various skin conditions, there remain gaps in the knowledge, specifically with respect to the contribution of S-palmitoylation to the maintenance of skin barrier function. Towards this goal, we performed PubMed literature searches relevant to S-palmitoylation in skin to define current knowledge and areas that may benefit from further research studies. Furthermore, to identify alterations in gene products that are S-palmitoylated, we utilized bioinformatic tools such as SwissPalm and analyzed relevant data from publicly available databases such as cBioportal. Since the targeting of S-palmitoylated targets may offer an innovative treatment perspective, we surveyed small molecules inhibiting zDHHCs, including 2-bromopalmitate (2-BP) which is associated with off-target effects, and other targeting strategies. Collectively, our work aims to advance both basic and clinical research on skin barrier function with a focus on zDHHCs and relevant protein targets that may contribute to the pathogenesis of skin conditions such as atopic dermatitis, psoriasis, and skin cancers including melanoma.

Contaminant-Associated Disruption of the Skin Transcriptome in the Endangered St. Lawrence Estuary Beluga

The St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) population in Canada is Endangered, and endocrine disrupting contaminants, such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and other halogenated flame retardants, have been identified as a threat to the recovery of this population. Here, potential impacts of these contaminants on SLE beluga were evaluated by comparing skin transcriptome profiles and biological pathways between this population and a population less exposed to contaminants (Eastern Beaufort Sea) used as a reference. Differential gene expression analysis indicated potential seasonal or geography-related (Arctic vs temperate regions) effects on the skin transcriptome. Among the gene transcripts that were associated with Σ31PCB (123 genes), Σ29PBDE (198 genes), HBB (347 genes), and PBEB (126 genes) blubber concentrations, several were related to immune response pathways. In addition, 18 toxicology-related gene transcripts selected from the literature were correlated with organohalogen concentrations and were used to derive new threshold values in beluga skin for potential biological effects of ΣPCB (1,500 ng/g lw), ΣPBDE (52 ng/g lw), and two other flame retardants, i.e., HBB (1.2 ng/g lw) and PBEB (0.04 ng/g lw). Results suggest that exposure to these organohalogens pose a risk to the immune system of SLE beluga.

Allergens in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with a complex relationship to allergens. While AD itself is not an allergic reaction and does not necessarily involve allergen sensitization, AD patients show higher rates of sensitization to food and inhalant allergens compared to the general population. Recent evidence refining the "dual allergen exposure hypothesis" demonstrates that early oral exposure to allergens through an intact gastrointestinal barrier typically promotes tolerance, while exposure through compromised skin or respiratory barriers often leads to sensitization. Therefore, the impaired skin barrier function in AD patients increases the risk of transcutaneous sensitization and may interfere with oral tolerance development. Interestingly, AD patients' sensitivity to contact allergens (such as metals and fragrances) is not necessarily higher than that of the general population, which may be related to the inherent properties of these allergens. Personalized allergen testing can help guide appropriate allergen avoidance and reintroduction strategies in AD management. The insights into optimal allergen exposure conditions have also expanded the potential applications of allergen-specific immunotherapy in preventing AD onset in high-risk populations and halting the atopic march.

Filaggrinopathies-FLG/FLG2: Diagnostic Complexities and Immunotherapy

FLG and FLG2 proteins are expressed in the outer layers of the epidermis, where they are vital in epidermal differentiation and skin barrier formation. Filaggrinopathies involving dysfunctions in these proteins are associated with a spectrum of phenotypic presentations, from monogenic to multifactorial conditions. This review examines biosynthesis and function of FLG and FLG2 proteins and evaluates their molecular pathogenesis in filaggrinopathies. Moreover, genotype-phenotype correlations are assessed, emphasizing genetic diagnosis complexities and diverse immune dysregulation patterns. Finally, it examines ongoing immunotherapeutic approaches by targeting different cytokines as promising treatment options for filaggrinopathies management.

Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial Structures

Reptiles, birds, mammals and amphibians, together forming the clade tetrapods, have a large diversity of cornified skin appendages, such as scales, feathers, hair and claws. The skin appendages consist of dead epithelial cells that are tightly packed with specific structural proteins. Here, we review the molecular diversity and expression patterns of major types of skin appendage proteins, namely keratin intermediate filament proteins, keratin-associated proteins (KRTAPs) and proteins encoded by genes of the epidermal differentiation complex (EDC), including corneous beta-proteins, also known as beta-keratins. We summarize the current knowledge about the components of skin appendages with a focus on keratins and EDC proteins that have recently been identified in reptiles and birds. We discuss gaps of knowledge and suggest directions of future research.

Improved prenatal assessment of kidney disease using multiple ultrasound features

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT), often discovered in utero, cover a wide spectrum of outcomes ranging from normal postnatal kidney function to foetal death. The current ultrasound workup does not allow for an accurate assessment of the outcome. The present study aimed to significantly improve the ultrasound-based prediction of postnatal kidney survival in CAKUT.

METHODS

Histological analysis of kidneys of 15 CAKUT foetuses was performed to better standardize the ultrasound interpretation of dysplasia and cysts. Ultrasound images of 140 CAKUT foetuses with 2-year postnatal follow-up were annotated for amniotic fluid volume and kidney number, size, dysplasia and/or cysts using a standardized ultrasound readout. Association of ultrasound features and clinical data (sex and age at diagnosis) with postnatal kidney function was studied using logistic regression. Amniotic fluid proteome related to kidney dysplasia or cysts was characterized by mass spectrometry.

RESULTS

Histologically, poor ultrasound corticomedullary differentiation was associated with dysplastic lesions and ultrasound hyperechogenicity was associated with the presence of microcysts. Of all ultrasound and clinical parameters, reduced amniotic volume, dysplasia and cysts were the best predictors of poor outcome (odds ratio 57 [95% confidence interval (CI) 11-481], 20 [3-225] and 7 [1-100], respectively). Their combination into an algorithm improved prediction of postnatal kidney function compared with amniotic volume alone (area under the receiver operating characteristics curve 0.92 [95% CI 0.86-0.98] in a 10-fold cross-validation). Dysplasia and cysts were correlated (Cramer's V coefficient = 0.44, P < .0001), but amniotic fluid proteome analysis revealed that they had a distinct molecular origin (extracellular matrix and cell contacts versus cellular death, respectively), probably explaining the additivity of their predictive performances.

CONCLUSION

Antenatal clinical advice for CAKUT pregnancies can be improved by a more standardized and combined interpretation of ultrasound data.

Anti-ageing mechanism of topical bioactive ingredient composition on skin based on network pharmacology

OBJECTIVE

To elucidate the anti-ageing mechanism of the combination of eight ingredients on the skin from a multidimensional view of the skin.

METHODS

The target pathway mechanisms of composition to delay skin ageing were investigated by a network pharmacology approach and experimentally validated at three levels: epidermal, dermal, and tissue.

RESULTS

We identified 24 statistically significant skin ageing-related pathways, encompassing crucial processes such as epidermal barrier repair, dermal collagen and elastin production, inhibition of reactive oxygen species (ROS), as well as modulation of acetylcholine and acetylcholine receptor binding. Furthermore, our in vitro experimental findings exhibited the following outcomes: the composition promotes fibroblast proliferation and the expression of barrier-related genes in the epidermis; it also stimulated the expression of collagen I, collagen III, and elastic fibre while inhibiting ROS and β-Gal levels in HDF cells within the dermis. Additionally, Spilanthol in the Acmella oleracea extract contained in the composition demonstrated neuro-relaxing activity in Zebrafish embryo, suggesting its potential as an anti-wrinkle ingredient at the hypodermis level.

CONCLUSIONS

In vitro experiments validated the anti-ageing mechanism of composition at multiple skin levels. This framework can be extended to unravel the functional mechanisms of other clinically validated compositions, including traditional folk recipes utilized in cosmeceuticals.

Biosensors for the detection of celiac disease

Celiac disease (CeD) is an autoimmune disorder triggered by sensitivity to gluten, a protein complex found in wheat, barley, and rye. Gliadins, a component of gluten, are proteins that trigger an immune response in individuals with CeD, primarily affecting the small intestine's inner lining. Despite a 1-1.5% prevalence, only 24% of cases are diagnosed due to non-specific symptoms. Screening is advised for high-risk groups, including first-degree relatives and type 1 diabetes patients. The accurate diagnosis of this condition and the assessment of the patient's response to the current treatment - a lifelong gluten-free diet - necessitate using dependable, swift, sensitive, specific, uncomplicated, and affordable analytical methods. Detecting CeD biomarkers in whole blood, serum, or plasma provides a non-invasive approach that serves as an ideal initial diagnostic step. Biosensors offer a novel and alternative way for CeD detection, began emerging in 2007, and hold promise for clinical and point-of-care applications. This review explores the use of biomarker-based diagnostic approaches for CeD, with a focus on biosensors. It delves into the progress of biosensors for CeD diagnosis, identifying trends and challenges in this evolving field. Key biomarkers are highlighted, offering insights into the evolving landscape of biosensors in CeD detection.

Spatial transcriptomics unveils estrogen-modulated immune responses and structural alterations in the ectocervical mucosa of depot medroxyprogesterone acetate users

The injectable contraceptive, depot medroxyprogesterone acetate (DMPA), is associated with compromised cervical mucosal barriers. High-resolution spatial transcriptomics is applied here to reveal the spatial localization of these altered molecular markers. Ectocervical tissue samples from Kenyan sex workers using DMPA, or non-hormonal contraceptives, underwent spatial transcriptomics and gene set enrichment analyses. Integrated systemic estradiol levels and bulk tissue gene expression data from a larger cohort enhanced the study's scope. Unsupervised clustering unveiled four epithelial and seven submucosal layers, showcasing spatially restricted and diverse functional epithelial responses, and a less structured submucosal spatial ordering. DMPA associated with mucosal-wide immunoglobulin gene upregulation, verified by CD20+ B-cell immunostaining, and upregulated immune markers adjacent to the basal membrane. Downregulated genes represented spatially restricted disrupted epithelial barrier integrity and submucosal extracellular matrix dysfunction. The transcriptional profile was associated with markers of estrogen regulation. Collectively, our findings reveal estrogen-modulated distinct ectocervical transcriptional profiles associated with DMPA usage. While upregulation of immunoglobulin genes occurs throughout the mucosa, activation of innate immune responses and dysregulation of barrier integrity markers are spatially restricted. These results extend previous analyses using bulk transcriptomics and provide insights into the molecular landscape influenced by DMPA, shedding light on contraceptive effects and health implications.

Convergent Evolution Has Led to the Loss of Claw Proteins in Snakes and Worm Lizards

The evolution of cornified skin appendages, such as hair, feathers, and claws, is closely linked to the evolution of proteins that establish the unique mechanical stability of these epithelial structures. We hypothesized that the evolution of the limbless body anatomy of the Florida worm lizard (Rhineura floridana) and the concomitant loss of claws had led to the degeneration of genes with claw-associated functions. To test this hypothesis, we investigated the evolution of three gene families implicated in epithelial cell architecture, namely type I keratins, type II keratins, and genes of the epidermal differentiation complex in R. floridana in comparison with other squamates. We report that the orthologs of mammalian hair and nail keratins have undergone pseudogenization in R. floridana. Likewise, the epidermal differentiation complex genes tentatively named EDYM1 and EDCCs have been lost in R. floridana. The aforementioned genes are conserved in various lizards with claws, but not in snakes. Proteomic analysis of the cornified claws of the bearded dragon (Pogona vitticeps) confirmed that type I and type II hair keratin homologs, EDYM1 and EDCCs, are protein components of claws in squamates. We conclude that the convergent evolution of a limbless body was associated with the convergent loss of claw keratins and differentiation genes in squamates.

Evaluation of the digestion protocol of mouse neonatal epidermis for single-cell RNA sequencing

The skin is primarily composed of keratinocytes and forms an effective barrier between the organism and external environment. Neonatal skin analysis is essential for understanding developmental processes and rare skin diseases. However, efficient single-cell dissociation methods for the neonatal mouse epidermis remain underexplored. Here, three enzymes (Trypsin, TrypLE, and Liberase) used for tissue dissociation were compared to optimize single-cell RNA sequencing (scRNA-seq) of the mouse neonatal epidermis. scRNA-seq revealed distinct differences in cell recovery between the enzymes, with Liberase enriching suprabasal keratinocytes and Trypsin/TrypLE favoring basal keratinocytes. Although all enzymes produced comparable data quality, the observed bias in cell population recovery highlights the significant impact of dissociation protocols on the scRNA-seq results. These findings highlight the importance and optimal selection of enzymes for the analysis of unbiased neonatal epidermis.

Guidelines for preparation and flow cytometry analysis of human nonlymphoid tissue DC

This article is part of the Dendritic Cell Guidelines article series, which provides a collection of state-of-the-art protocols for the preparation, phenotype analysis by flow cytometry, generation, fluorescence microscopy, and functional characterization of mouse and human dendritic cells (DC) from lymphoid organs, and various nonlymphoid tissues. Within this article, detailed protocols are presented that allow for the generation of single-cell suspensions from human nonlymphoid tissues including lung, skin, gingiva, intestine as well as from tumors and tumor-draining lymph nodes with a subsequent analysis of dendritic cells by flow cytometry. Further, prepared single-cell suspensions can be subjected to other applications including cellular enrichment procedures, RNA sequencing, functional assays, etc. While all protocols were written by experienced scientists who routinely use them in their work, this article was also peer-reviewed by leading experts and approved by all co-authors, making it an essential resource for basic and clinical DC immunologists.

Regulation of epidermal barrier function and pathogenesis of psoriasis by serine protease inhibitors

Serine protease inhibitors (Serpins) are a protein superfamily of protease inhibitors that are thought to play a role in the regulation of inflammation, immunity, tumorigenesis, coagulation, blood pressure and cancer metastasis. Serpins is enriched in the skin and play a vital role in modulating the epidermal barrier and maintaining skin homeostasis. Psoriasis is a chronic inflammatory immune-mediated skin disease. At present, most serpins focus on the pathogenesis of psoriasis vulgaris. Only a small number, such as the mutation of SerpinA1/A3/B3, are involved in the pathogenesis of GPP. SerpinA12 and SerpinG1 are significantly elevated in the serum of patients with psoriatic arthritis, but their specific mechanism of action in psoriatic arthritis has not been reported. Some Serpins, including SerpinA12, SerpinB2/B3/B7, play multiple roles in skin barrier function and pathogenesis of psoriasis. The decrease in the expression of SerpinA12, SerpinB7 deficiency and increase in expression of SerpinB3/4 in the skin can promote inflammation and poor differentiation of keratinocyte, with damaged skin barrier. Pso p27, derived from SerpinB3/B4, is an autoantigen that can enhance immune response in psoriasis. SerpinB2 plays a role in maintaining epidermal barrier integrity and inhibiting keratinocyte proliferation. Here we briefly introduce the structure, functional characteristics, expression and distribution of serpins in skin and focus on the regulation of serpins in the epidermal barrier function and the pathogenic role of serpins in psoriasis.

Amygdalin alleviates psoriasis-like lesions by improving skin barrier function

Psoriasis is a chronic, relapsing, inflammatory skin disease that is caused by the immune system. Amygdalin possesses immune-modulating and anti-inflammatory effects. To explore the possible effects of amygdalin on psoriasis and its pathogenesis of action, we examined the effects of amygdalin on imiquimod-induced psoriasis, tape-stripping-induced skin barrier disruption, and investigated the potential mechanism of action in vitro. The fact that amygdalin could reduce the thickness of the epidermis and inflammatory cell infiltration in two animal models inhibited the production of IL-1β, IL-6, and TNF-a, and the expression of filaggrin, involucrin, and keratin10 was increased. Also, in IL-17 A and TNF-α induced HaCaT, amygdalin inhibits the expression of IL-6, IL-1β, and TNF-a, promoting the expression of skin barrier recovery-related proteins flaggrin, involucrin, and keratin10. Combined in vivo and in vitro experiments suggest that amygdalin modulates inflammation and the skin barrier in psoriasis. The same study also conducted a preliminary mechanistic exploration and found that amygdalin inhibited the phosphorylation of the p38MAPK signaling pathway. In conclusion, Amygdalin can alleviate psoriasis lesions and improve skin barrier impairment, and the research provides an experimental basis for its future development as a drug candidate for psoriasis therapy.

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

Background

The 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.

Objectives

The purpose of the study was to characterize the barrier function of ex vivo models of damaged human skin.

Methods

Skin 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 discussion

The 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.

Holistic investigation of the anti-wrinkle and repair efficacy of a facial cream enriched with C-xyloside

OBJECTIVE

To investigate the repairing and anti-wrinkle efficacy of the facial cream enriched with C-xyloside, aiming at comprehensively evaluating its skin anti- aging effect and clarify its potential mechanism of action.

METHODS

The repairing efficacy was studied on 3D epidermis skin model and the antiaging efficacy was studied on ex-vivo human skin. Two clinical studies were conducted with Chinese females. In the first study, 49 subjects aged between 30 and 50 with wrinkle concerns were recruited and instructed to apply the investigational cream containing C-xyloside for 8 weeks. Wrinkles attributes were assessed by dermatologist. Instrumental measurements on skin hydration, trans-epidermal water loss (TEWL), and skin elasticity were also conducted. In the second study, 30 subjects aged between 25 and 60 with self-declared sensitive skin and facial redness were recruited and instructed to apply the cream for 4 weeks. Biomarker analysis of the stratum corneum was conducted through facial tape strips.

RESULTS

The cream improved the histomorphology of the 3D epidermis skin model after SLS stimulation, and significantly increase the expression of LOR and FLG. On human skin, the cream improved the histopathology induced by UV, and significantly increased the protein content of COL I and COL III, collagen density and the number of Ki-67 positive cell of skin compared with model group (n = 3, p < 0.01). The results from the first clinical study demonstrate a significant increased the skin hydration and elasticity by 21.90%, 13.08% (R2) and 12.30% (R5), respectively (n = 49, p < 0.05), and the TEWL values decreased by 33.94% (n = 49, p < 0.05), after 8 weeks application of the cream. In addition, the scores for nasolabial folds, glabellar wrinkle, underneath eye wrinkles, crow's feet wrinkle and forehead wrinkle in the volunteers exhibited a significant reduction of 34.02%, 43.34%, 50.03%, 33.64% and 55.81% respectively (n = 49, p < 0.05). The (rCE)/(fCE) ratio of volunteers based on tape stripping significant increased after using the sample cream (n = 30, p < 0.05).

CONCLUSION

The cream containing C-xyloside showed improvement of skin wrinkles and enhancement of skin barrier function. These efficacies may be attributed to the fact that the sample cream can increase the expression of skin barrier related proteins LOR and FLG, promote the maturation of cornified envelope, enhance collagen I and III protein expression and stimulate skin cell proliferation, to provide sufficient evidence supporting its antiaging efficacy of skin.

An updated review of HSV-1 infection-associated diseases and treatment, vaccine development, and vector therapy application

Herpes simplex virus type 1 (HSV-1) is a globally widespread virus that causes and associates with a wide range of diseases, including herpes simplex encephalitis, herpes simplex keratitis, and herpes labialis. The interaction between HSV-1 and the host involves complex immune response mechanisms, including recognition of viral invasion, maintenance of latent infection, and triggering of reactivation. Antiviral therapy is the core treatment for HSV-1 infections. Meanwhile, vaccine development employs different strategies and methods, and several promising vaccine types have emerged, such as live attenuated, protein subunit, and nucleic acid vaccines, offering new possibilities for the prevention of HSV-1 infection. Moreover, HSV-1 can be modified into a therapeutic vector for gene therapy and tumour immunotherapy. This review provides an in-depth summary of HSV-1 infection-associated innate and adaptive immune responses, disease pathogenesis, current therapeutic approaches, recent advances in vaccine development, and vector therapy applications for cancer treatment. Through a systematic review of multiple aspects of HSV-1, this study aims to provide a comprehensive and detailed reference for the public on the prevention, control, and treatment of HSV-1.

Immunomodulatory potential of primary cilia in the skin

Primary cilia (PC) are essential signaling hubs for proper epithelial formation and the maintenance of skin homeostasis. Found on most cells in the human body, including skin cells, PC facilitate signal transduction that allows ciliated cells to interact with the immune system via multiple pathways, helping to maintain immune system homeostasis. PC can be altered by various microenvironmental stimuli to develop corresponding regulatory functions. Both PC and ciliary signaling pathways have been shown to be involved in the immune processes of various skin lesions. However, the mechanisms by which PC regulate cellular functions and maintain immune homeostasis in tissues are highly complex, and our understanding of them in the skin remains limited. In this paper, we discuss key ciliary signaling pathways and ciliated cells in the skin, with a focus on their immunomodulatory functions. We have compiled evidence from various cells, tissues and disease models to help explore the potential immunomodulatory effects of PC in the skin and their molecular mechanisms.

Novel Exosomal miRNA Expression in Irradiated Human Keratinocytes

The epidermis, the outer layer of the skin, relies on a delicate balance of cell growth and keratinocyte differentiation for its function and renewal. Recent research has shed light on exosomes' role in facilitating skin communication by transferring molecules like miRNAs, which regulate gene expression post-transcriptionally. Additionally, these factors lead to skin aging through oxidative stress caused by reactive oxygen species (ROS). In this research project, experiments were conducted to study the impact of Sun2000 solar simulator irradiation on exosomal miRNA profiles in HEKa cells. We hypothesized that acute oxidative stress induced by solar simulator irradiation would alter the expression profile of exosomal miRNAs in HEKa cells. The cells were exposed to different durations of irradiation to induce oxidative stress, and the levels of reactive ROS were measured using the CellROX Deep Red flow cytometry assay kit. Exosomes were isolated from both control and irradiated cells, characterized using DLS and SEM techniques, and their miRNAs were extracted and analyzed using qPCR. Solar simulator irradiation led to a time-dependent increase in intracellular ROS and a decrease in cell viability. Exosomal size increased in irradiated cells. Fifty-nine exosomal miRNAs were differentially expressed in irradiated HEKa cells, including hsa-miR-425-5p, hsa-miR-181b-5p, hsa-miR-196b-5p, hsa-miR-376c-3p, and hsa-miR-15a-5p. This study highlights the significant impact of solar radiation on exosomal miRNA expression in keratinocytes, suggesting their potential role in the cellular response to oxidative stress.

Evaluation of physical and chemical modifications to drug reservoirs for stimuli-responsive microneedles

Hydrogel-forming microneedle (MN) arrays are minimally-invasive devices that can penetrate the stratum corneum, the main barrier to topical drug application, without causing pain. However, drug delivery using hydrogel-forming MN arrays tends to be relatively slow compared to rapid drug delivery using conventional needles and syringes. Therefore, in this work, for the first time, different physical and chemical delivery enhancement methods were employed in combination with PVA-based hydrogel-forming MN arrays. Using a model drug, ibuprofen (IBU) sodium, the designed systems were assessed in terms of the extent of transdermal delivery. Iontophoresis (ITP) and heat-assisted drug delivery technology were investigated as physical permeation enhancement techniques. Ex vivo studies demonstrated that the ITP (0.5 mA/cm2)-mediated combination strategy significantly enhanced the transdermal permeation of IBU sodium over the first 6 h (~ 5.11 mg) when compared to MN alone (~ 1.63 mg) (p < 0.05). In contrast, heat-assisted technology showed almost no promoting effect on transdermal delivery. Furthermore, IBU sodium-containing rapidly dissolving lyophilised and effervescent reservoirs, classified as chemical modification methods, were prepared. Both strategies achieved rapid and effective ex vivo IBU sodium permeation, equating to ~ 78% (30.66 mg) and ~ 71% (28.43 mg) from lyophilised and effervescent reservoirs, respectively. Moreover, in vivo pharmacokinetic studies showed that the IBU sodium plasma concentration within lyophilised and effervescent groups reached a maximum concentration (Cmax) at 4 h (~ 282.15 µg/mL) and 6 h (~ 140.81 µg/mL), respectively. These strategies not only provided rapid achievement of therapeutic levels (10-15 µg/ml), but also resulted in sustained release of IBU sodium for at least 48 h, which could effectively reduce the frequency of administration, thereby improving patient compliance and reducing side effects of IBU sodium.

Impact of blue light on cutaneous barrier structures and properties: NPLC/HR-MSn and Raman analyses

Skin health relies heavily on a well-maintained cutaneous barrier. While the detrimental effects of UV radiation on the epidermis are established, the impact of blue light, a significant component of sunlight and artificial sources, is less clear. This study aims to explore blue light's influence on the reconstructed human epidermis (RHE) using two complementary analytical approaches: Raman microspectroscopy and normal phase liquid chromatography coupled with high-resolution mass spectrometry (NPLC/HR-MSn). RHE samples were exposed to blue light (415 nm and 455 nm) during different stages of their maturation. Raman spectra were acquired for both irradiated and non-irradiated (control) samples. Raman descriptors were analyzed to assess potential alterations in the structural organization of proteins and lipids' conformational changes. Additionally, lipids from RHE samples were extracted and analyzed using NPLC/HR-MSn. Blue light exposure led to changes in the structural organization of RHE lipids and proteins, as well as changes in the lipid composition. These changes varied depending on the wavelength and exposure dose. Exposure to blue light could disrupt the integrity of the skin's protective barrier, leading to increased sensitivity to environmental stressors and potential skin damage.

Survival prediction in patients with head and neck squamous cell carcinoma and novel mechanistic insights of S100A8/A9

BACKGROUND

S100A8/A9, an innate immune protein, significantly regulates inflammatory processes and immune responses. While S100A8/A9 has been linked to various diseases, its association with head and neck squamous cell carcinoma (HNSCC) remains unclear.

METHODS

Samples from the Cancer Genome Atlas (TCGA) were categorized into groups with low and high expression of S100A8/A9. R software, Sangerbox, UALCAN, GEPIA2, STRING, Cytoscape, TCGC Data Portal, miRcode, OncomiR and ENCORI databases were used to comprehensively study the expression, interactome and mutational profiles of S100A8/A9 and associated mechanism in HNSCC.

RESULTS

The proteins S100A8/A9 were found to be associated with processes of 'epithelium development', 'regulating pluripotency of stem cells' and 'regulation of immune system'. The most frequent mutation observed in the S100A8 protein was E93K (3/37, MU4401889), while for the S100A9 protein, it was R10C (4/37, MU4633862). Furthermore, the group expressing high levels of S100A8/A9 showed increased infiltration by dendritic cells and neutrophils, but decreased infiltration by M2 macrophages, compared to the group with low S100A8/A9 expression. S100A8/A9 was also found to interact with a variety of mRNA transcripts, several of which were involved in initiation and progression of HNSCC. Through LASSO-Cox method, 20 genes (CALML5, MSX1, FZD3, STC2, SLC2A3, TMEM198B, DYNC1I1, SPHK2, ALMS1.IT1, SPPL2B, PDGFA, BCORL1, TEX101, SGCE, DNAJC12, RRN3P1, HOXB9, TMEM150C, METTL7B and PSPN) were screening to construct a prognostic model to distinguish favorable and poor prognosis of HNSCC patients. Besides, our prognostic model was also validated in GSE41613 cohort.

CONCLUSIONS

S100A8/A9 may be a promising marker for the diagnostic and prognostic assessment of the HNSCC patients. Based on these insights, we have devised a new classification model for HNSCC, which has the potential to enhance the management and personalized treatment of HNSCC patients. The model should also be further optimized through the expansion of sample size and implemented experimental studies in future research.

Cell differentiation in the embryonic periderm and in scaffolding epithelia of skin appendages

Terminal differentiation of epithelial cells is critical for the barrier function of the skin, the growth of skin appendages, such as hair and nails, and the development of the skin of amniotes. Here, we present the hypothesis that the differentiation of cells in the embryonic periderm shares characteristic features with the differentiation of epithelial cells that support the morphogenesis of cornified skin appendages during postnatal life. The periderm prevents aberrant fusion of adjacent epithelial sites during early skin development. It is shed off when keratinocytes of the epidermis form the cornified layer, the stratum corneum. A similar role is played by epithelia that ensheath cornifying skin appendages until they disintegrate to allow the separation of the mature part of the skin appendage from the adjacent tissue. These epithelia, exemplified by the inner root sheath of hair follicles and the epithelia close to the free edge of nails or claws, are referred to as scaffolding epithelia. The periderm and scaffolding epithelia are similar with regard to their transient functions in separating tissues and the conserved expression of trichohyalin and trichohyalin-like genes in mammals and birds. Thus, we propose that parts of the peridermal differentiation program were coopted to a new postnatal function during the evolution of cornified skin appendages in amniotes.

Role of fibroblasts in nonfibrotic autoimmune skin diseases

Autoimmune diseases, a disease characterized by immune imbalance caused by the human immune system mistakenly attacking its own components, include vitiligo, psoriasis and atopic dermatitis (AD). Previous studies on autoimmune diseases have focused mainly on immune cells, keratinocytes and endothelial cells. Fibroblasts, the main cells that secrete the extracellular matrix (ECM) in the dermis, have been studied thoroughly in terms of fibrosis and wound healing. However, an increasing number of studies have shown that fibroblasts play an important role in nonfibrotic autoimmune skin diseases. In this article, the previously reported role of fibroblasts in nonfibrous autoimmune skin diseases such as psoriasis, vitiligo and AD is summarized to provide new ideas for the treatment of this disease.

Autophagy-Mediated Cellular Remodeling during Terminal Differentiation of Keratinocytes in the Epidermis and Skin Appendages

The epidermis of the skin and skin appendages, such as nails, hair and sebaceous glands, depend on a balance of cell proliferation and terminal differentiation in order to fulfill their functions at the interface of the body and the environment. The differentiation of epithelial cells of the skin, commonly referred to as keratinocytes, involves major remodeling processes that generate metabolically inactive cell remnants serving as building blocks of the epidermal stratum corneum, nail plates and hair shafts. Only sebaceous gland differentiation results in cell disintegration and holocrine secretion. A series of studies performed in the past decade have revealed that the lysosome-dependent intracellular degradation mechanism of autophagy is active during keratinocyte differentiation, and the blockade of autophagy significantly alters the properties of the differentiation products. Here, we present a model for the autophagy-mediated degradation of organelles and cytosolic proteins as an important contributor to cellular remodeling in keratinocyte differentiation. The roles of autophagy are discussed in comparison to alternative intracellular degradation mechanisms and in the context of programmed cell death as an integral end point of epithelial differentiation.

Upregulation of keratin 15 is required for varicella-zoster virus replication in keratinocytes and is attenuated in the live attenuated vOka vaccine strain

Varicella-zoster virus (VZV) is the etiological agent of chickenpox and shingles, diseases characterised by epidermal virus replication in skin and mucosa and the formation of blisters. We have previously shown that VZV infection has a profound effect on keratinocyte differentiation, altering the normal pattern of epidermal gene expression. In particular, VZV infection reduces expression of suprabasal keratins 1 and 10 and desmosomal proteins, disrupting epidermal structure to promote expression of a blistering phenotype. Here, we extend these findings to show that VZV infection upregulates the expression of keratin 15 (KRT15), a marker expressed by basal epidermal keratinocytes and hair follicles stem cells. We demonstrate that KRT15 is essential for VZV replication in the skin, since downregulation of KRT15 inhibits VZV replication in keratinocytes, while KRT15 exogenous overexpression supports viral replication. Importantly, our data show that VZV upregulation of KRT15 depends on the expression of the VZV immediate early gene ORF62. ORF62 is the only regulatory gene that is mutated in the live attenuated VZV vaccine and contains four of the five fixed mutations present in the VZV Oka vaccine. Our data indicate that the mutated vaccine ORF62 is not capable of upregulating KRT15, suggesting that this may contribute to the vaccine attenuation in skin. Taken together our data present a novel association between VZV and KRT15, which may open a new therapeutic window for a topical targeting of VZV replication in the skin via modulation of KRT15.

Pharmacological Impacts of Mucopolysacccharide Polyphosphates in the Epidermis Involves Inhibition of Amphiregulin-Mediated Signals in Keratinocytes

The epidermis, the most superficial layer of the human skin, serves a critical barrier function, protecting the body from external pathogens and allergens. Dysregulation of epidermal differentiation contributes to barrier dysfunction and has been implicated in the pathology of various dermatological diseases, including atopic dermatitis (AD). Mucopolysaccharide polysulphate (MPS) is a moisturising agent used to treat xerosis in patients with AD. However, its mechanism of action on keratinocytes, the main constituents of the epidermis, remains unclear. In this study, we investigated the effect of MPS on keratinocytes by subjecting adult human epidermal and three-dimensional cultured keratinocytes to MPS treatment, followed by transcriptome analysis. The analysis revealed that MPS treatment enhances keratinocyte differentiation and suppresses proliferation. We focused on amphiregulin (AREG), a membrane protein that belongs to the epidermal growth factor (EGF) family and possesses a heparin-binding domain, as a significant target among the genes altered by MPS. MPS exerted an inhibitory effect directly on AREG, rather than on EGF receptors or other members of the EGF family. Furthermore, AREG leads to a reduction in epidermal barrier function, whereas MPS contributes to barrier enhancement via AREG inhibition. Collectively, these findings suggest that MPS modulates barrier function through AREG inhibition, offering insights into potential therapeutic strategies for skin barrier restoration.

Strengthening the Skin Barrier by Using a Late Cornified Envelope 6A-Derived Biomimetic Peptide

Changes in the expression of cornified envelope (CE) components are a hallmark of numerous pathological skin conditions and aging, underlying the importance of this stratum corneum structure in the homeostasis of the epidermal barrier. We performed a detailed characterisation of LCE6A, a member of the Late Cornified Envelope protein family. Immunohistochemical and immunoblot experiments confirmed that LCE6A is expressed late during epidermal differentiation. Crosslinking assays of recombinant LCE6A performed either in situ on human skin sections or in vitro demonstrated that LCE6A is indeed a substrate of transglutaminases and crosslinked to CEs. LCE6A-derived peptides containing a glutamine-lysine sequence retained these properties of the full-length protein and reinforced the mechanical resistance of CE submitted to sonication. We designed P26, a LCE6A-derived biomimetic peptide that similarly reinforced CE in vitro, and evaluated its protective properties ex vivo, on human skin explants, and in two double blind and vehicle-controlled clinical trials. P26 was able to protect the skin from barrier disruption, to limit the damage resulting from a defective barrier, and could improve the signs of aging such as loss of skin firmness and increased skin roughness. Hence, our detailed characterisation of LCE6A as a component of the CE enabled us to develop a LCE6A-derived peptide, biologically active with a new and original mode of action that could be of great interest as a cosmetic ingredient and a pharmacologic agent.

Transglutaminase 1: Emerging Functions beyond Skin

Transglutaminase enzymes catalyze Ca2+- and thiol-dependent posttranslational modifications of glutamine-residues that include esterification, hydrolysis and transamidation, which results in covalent protein-protein crosslinking. Among the eight transglutaminase family members in mammals, transglutaminase 1 (TG1) plays a crucial role in skin barrier formation via crosslinking and insolubilizing proteins in keratinocytes. Despite this established function in skin, novel functions have begun merging in normal tissue homeostasis as well as in pathologies. This review summarizes our current understanding of the structure, activation, expression and activity patterns of TG1 and discusses its putative novel role in other tissues, such as in vascular integrity, and in diseases, such as cancer and fibrosis.

Effect of Staphylococcus aureus colonization and immune defects on the pathogenesis of atopic dermatitis

Atopic dermatitis (AD) is a common and recurrent skin disease characterized by skin barrier dysfunction, inflammation and chronic pruritus, with wide heterogeneity in terms of age of onset, clinical course and persistence over the lifespan. Although the pathogenesis of the disease are unclear, epidermal barrier dysfunction, immune and microbial dysregulation, and environmental factors are known to be critical etiologies in AD pathology. The skin microbiota represents an ecosystem consisting of numerous microbial species that interact with each other as well as host epithelial cells and immune cells. Although the skin microbiota benefits the host by supporting the basic functions of the skin and preventing the colonization of pathogens, disruption of the microbial balance (dysbiosis) can cause skin diseases such as AD. Although AD is a dermatological disease, recent evidence has shown that changes in microbiota composition in the skin and intestine contribute to the pathogenesis of AD. Environmental factors that contribute to skin barrier dysfunction and microbial dysbiosis in AD include allergens, diet, irritants, air pollution, epigenetics and microbial exposure. Knowing the microbial combination of intestin, as well as the genetic and epigenetic determinants associated with the development of autoantibodies, may help elucidate the pathophysiology of the disease. The skin of patients with AD is characterized by microbial dysbiosis as a result of reduced microbial diversity and overgrowth of the pathogens such as Staphylococcus aureus. Recent studies have revealed the importance of building a strong immune response against microorganisms during childhood and new mechanisms of microbial community dynamics in modulating the skin microbiome. Numerous microorganisms are reported to modulate host response through communication with keratinocytes, specific immune cells and adipocytes to improve skin health and barrier function. This growing insight into bioactive substances in the skin microbiota has led to novel biotherapeutic approaches targeting the skin surface for the treatment of AD. This review will provide an updated overview of the skin microbiota in AD and its complex interaction with immune response mechanisms, as well as explore possible underlying mechanisms in the pathogenesis of AD and provide insights into new therapeutic developments for the treatment of AD. It also focuses on restoring skin microbial homeostasis, aiming to reduce inflammation by repairing the skin barrier.

Epidermal Differentiation Genes of the Common Wall Lizard Encode Proteins with Extremely Biased Amino Acid Contents

The epidermal differentiation complex (EDC) is a cluster of genes that code for protein components of cornified cells on the skin surface of amniotes. Squamates are the most species-rich clade of reptiles with skin adaptations to many different environments. As the genetic regulation of the skin epidermis and its evolution has been characterized for only a few species so far, we aimed to determine the organization of the EDC in a model species of squamates, the common wall lizard (Podarcis muralis). By comparative genomics, we identified EDC genes of the wall lizard and compared them with homologs in other amniotes. We found that the EDC of the wall lizard has undergone a major rearrangement leading to a unique order of three ancestral EDC segments. Several subfamilies of EDC genes, such as those encoding epidermal differentiation proteins containing PCCC motifs (EDPCCC) and loricrins, have expanded by gene duplications. Most of the EDPCCC proteins have cysteine contents higher than 50%, whereas glycine constitutes more than 50% of the amino acid residues of loricrin 1. The extremely biased amino acid compositions indicate unique structural properties of these EDC proteins. This study demonstrates that cornification proteins of the common wall lizard differ from homologous proteins of other reptiles, illustrating the evolutionary dynamics of diversifying evolution in squamates.

Dermal Injection of Recombinant Filaggrin-2 Ameliorates UVB-Induced Epidermal Barrier Dysfunction and Photoaging

The epidermal barrier is vital for protecting the skin from environmental stressors and ultraviolet (UV) radiation. Filaggrin-2 (FLG2), a critical protein in the stratum corneum, plays a significant role in maintaining skin barrier homeostasis. However, the precise role of FLG2 in mitigating the adverse effects of UV-induced barrier disruption and photoaging remains poorly understood. In this study, we revealed that UVB exposure resulted in a decreased expression of FLG2 in HaCaT keratinocytes, which correlated with a compromised barrier function. The administration of recombinant filaggrin-2 (rFLG2) enhanced keratinocyte differentiation, bolstered barrier integrity, and offered protection against apoptosis and oxidative stress induced by UVB irradiation. Furthermore, in a UV-induced photodamage murine model, the dermal injection of rFLG2 facilitated the enhanced restoration of the epidermal barrier, decreased oxidative stress and inflammation, and mitigated the collagen degradation that is typical of photoaging. Collectively, our findings suggested that targeting FLG2 could be a strategic approach to prevent and treat skin barrier dysfunction and combat the aging effects associated with photoaging. rFLG2 emerges as a potentially viable therapy for maintaining skin health and preventing skin aging processes amplified by photodamage.

VAMP2 controls murine epidermal differentiation and carcinogenesis by regulation of nucleophagy

Differentiation of murine epidermal stem/progenitor cells involves the permanent withdrawal from the cell cycle, the synthesis of various protein and lipid components for the cornified envelope, and the controlled dissolution of cellular organelles and nuclei. Deregulated epidermal differentiation contributes to the development of various skin diseases, including skin cancers. With a genome-wide shRNA screen, we identified vesicle-associated membrane protein 2 (VAMP2) as a critical factor involved in skin differentiation. Deletion of VAMP2 leads to aberrant skin stratification and enucleation in vivo. With quantitative proteomics, we further identified an autophagy protein, focal adhesion kinase family interacting protein of 200 kDa (FIP200), as a binding partner of VAMP2. Additionally, we showed that both VAMP2 and FIP200 are critical for murine keratinocyte enucleation and epidermal differentiation. Loss of VAMP2 or FIP200 enhances cutaneous carcinogenesis in vivo. Together, our findings identify important molecular mechanisms underlying epidermal differentiation and skin tumorigenesis.

Combined exposure to UV and PM affect skin oxinflammatory responses and it is prevented by antioxidant mix topical application: Evidences from clinical study

BACKGROUND

Exposure to environmental stressors like particulate matter (PM) and ultraviolet radiation (UV) induces cutaneous oxidative stress and inflammation and leads to skin barrier dysfunction and premature aging. Metals like iron or copper are abundant in PM and are known to contribute to reactive oxygen species (ROS) production.

AIMS

Although it has been suggested that topical antioxidants may be able to help in preventing and/or reducing outdoor skin damage, limited clinical evidence under real-life exposure conditions have been reported. The aim of the present study was to evaluate the ability of a topical serum containing 15% ascorbic acid, 0.5% ferulic acid, and 1% tocopherol (CF Mix) to prevent oxinflammatory skin damage and premature aging induced by PM + UV in a human clinical trial.

METHODS

A 4-day single-blinded, clinical study was conducted on the back of 15 females (18-40 years old). During the 4 consecutive days, the back test zones were treated daily with or without the CF Mix, followed by with/without 2 h of PM and 5 min of UV daily exposure.

RESULTS

Application of the CF Mix prevented PM + UV-induced skin barrier perturbation (Involucrin and Loricrin), lipid peroxidation (4HNE), inflammatory markers (COX2, NLRP1, and AhR), and MMP9 activation. In addition, CF Mix was able to prevent Type I Collagen loss.

CONCLUSION

This is the first human study confirming multipollutant cutaneous damage and suggesting the utility of a daily antioxidant topical application to prevent pollution induced skin damage.

Cell death as an architect of adult skin stem cell niches

Our skin provides a physical and immunological barrier against dehydration and environmental insults ranging from microbial attacks, toxins and UV irradiation to wounding. Proper functioning of the skin barrier largely depends on the interplay between keratinocytes- the epithelial cells of the skin- and immune cells. Two spatially distinct populations of keratinocyte stem cells (SCs) maintain the epidermal barrier function and the hair follicle. These SCs are inherently long-lived, but cell death can occur within their niches and impacts their functionality. The default cell death programme in skin is apoptosis, an orderly and non-inflammatory suicide programme. However, recent findings are shedding light on the significance of various modes of regulated necrotic cell death, which are lytic and can provoke inflammation within the local skin environment. While the presence of dying cells was generally regarded as a mere consequence of inflammation, findings in various human dermatological conditions and experimental mouse models of aberrant cell death control demonstrated that cell death programmes in keratinocytes (KCs) can drive skin inflammation and even tumour initiation. When cells die, they need to be removed by phagocytosis and KCs can function as non-professional phagocytes of apoptotic cells with important implications for their SC capacities. It is becoming apparent that in conditions of heightened SC activity, distinct cell death modalities differentially impact the different skin SC populations in their local niches. Here, we describe how regulated cell death modalities functionally affect epidermal SC niches along with their relevance to injury repair, inflammatory skin disorders and cancer.

Skin Development and Disease: A Molecular Perspective

Skin, the largest organ in the human body, is a crucial protective barrier that plays essential roles in thermoregulation, sensation, and immune defence. This complex organ undergoes intricate processes of development. Skin development initiates during the embryonic stage, orchestrated by molecular cues that control epidermal specification, commitment, stratification, terminal differentiation, and appendage growth. Key signalling pathways are integral in coordinating the development of the epidermis, hair follicles, and sweat glands. The complex interplay among these pathways is vital for the appropriate formation and functionality of the skin. Disruptions in multiple molecular pathways can give rise to a spectrum of skin diseases, from congenital skin disorders to cancers. By delving into the molecular mechanisms implicated in developmental processes, as well as in the pathogenesis of diseases, this narrative review aims to present a comprehensive understanding of these aspects. Such knowledge paves the way for developing innovative targeted therapies and personalised treatment approaches for various skin conditions.

Correlations between Skin Condition Parameters and Ceramide Profiles in the Stratum Corneum of Healthy Individuals

Ceramides are essential lipids for skin barrier function, and various classes and species exist in the human stratum corneum (SC). To date, the relationship between skin conditions and ceramide composition in healthy individuals has remained largely unclear. In the present study, we measured six skin condition parameters (capacitance, transepidermal water loss, scaliness, roughness, multilayer exfoliation, and corneocyte cell size) for the SC of the cheeks and upper arms of 26 healthy individuals and performed correlation analyses with their SC ceramide profiles, which we measured via liquid chromatography-tandem mass spectrometry. In the cheeks, high levels and/or ratios of two free ceramide classes containing an extra hydroxyl group in the long-chain moiety and a protein-bound ceramide class containing 6-hydroxysphingosine correlated with healthy skin conditions. In contrast, the ratios of two other free ceramide classes, both containing sphingosine, and a protein-bound ceramide class containing 4,14-sphingadiene correlated with unhealthy skin conditions, as did shortening of the carbon chain of the fatty acid portion of two ceramide classes containing non-hydroxy fatty acids. Thus, our findings help to elucidate the relationship between skin conditions and ceramide composition.