Functional properties and skin care effects of sodium trehalose sulfate.

BACKGROUND: It is known that heparinoid, a mucopolysaccharide polysulfate, is effective in improving rough skin and promoting blood circulation as medicines for diseased areas. However, heparinoid has a molecular weight of more than 5000 and cannot penetrate healthy stratum corneum. OBJECTIVE: We tested the efficacy of sulfated oligosaccharides with a molecular weight of less than 2000 on the human skin barrier function and moisturizing function. METHODS: We measured the transepidermal water loss (TEWL) of a three-dimensional human epidermis model cultured for 3 days after topical application of sulfated oligosaccharides, then observed the effects on TEWL suppression. The mRNA levels of proteins involved in intercellular lipid transport and storage in the stratum corneum, and moisture retention were measured using RT-qPCR. RESULTS: An increase in the mRNA levels of the ATP-binding cassette subfamily A member 12 (ABCA12), which transports lipids into stratum granulosum, was confirmed. Increases were also observed in the mRNA levels of filaggrin (FLG), which is involved in the generation of natural moisturizing factors, and of caspase-14, calpain-1 and bleomycin hydrolase, which are involved in the degradation of FLG. Antibody staining confirmed that the application of sodium trehalose sulfate to 3D model skin resulted in more ABCA12, ceramide, transglutaminase1, and FLG than those in controls. In a randomized, placebo-controlled, double-blind study, participants with low stratum corneum water content applied a lotion and emulsion containing sodium trehalose sulfate to their faces for 4 weeks. Sodium trehalose sulfate decreased the TEWL and increased the stratum corneum water content. CONCLUSION: These results suggest that cosmetics containing sodium trehalose sulfate act on the epidermis by increasing barrier factors and moisturizing factors, thereby ameliorating dry skin.

The retinoid X receptor has a critical role in synthetic rexinoid-induced increase in cellular all-trans-retinoic acid.

Rexinoids are agonists of nuclear rexinoid X receptors (RXR) that heterodimerize with other nuclear receptors to regulate gene transcription. A number of selective RXR agonists have been developed for clinical use but their application has been hampered by the unwanted side effects associated with the use of rexinoids and a limited understanding of their mechanisms of action across different cell types. Our previous studies showed that treatment of organotypic human epidermis with the low toxicity UAB30 and UAB110 rexinoids resulted in increased steady-state levels of all-trans-retinoic acid (ATRA), the obligatory ligand of the RXR-RAR heterodimers. Here, we investigated the molecular mechanism underlying the increase in ATRA levels using a dominant negative RXRα that lacks the activation function 2 (AF-2) domain. The results demonstrated that overexpression of dnRXRα in human organotypic epidermis markedly reduced signaling by resident ATRA, suggesting the existence of endogenous RXR ligand, diminished the biological effects of UAB30 and UAB110 on epidermis morphology and gene expression, and nearly abolished the rexinoid-induced increase in ATRA levels. Global transcriptome analysis of dnRXRα-rafts in comparison to empty vector-transduced rafts showed that over 95% of the differentially expressed genes in rexinoid-treated rafts constitute direct or indirect ATRA-regulated genes. Thus, the biological effects of UAB30 and UAB110 are mediated through the AF-2 domain of RXRα with minimal side effects in human epidermis. As ATRA levels are known to be reduced in certain epithelial pathologies, treatment with UAB30 and UAB110 may represent a promising therapy for normalizing the endogenous ATRA concentration and signaling in epithelial tissues.

Culture insert device with perfusable microchannels enhancesin vitroskin model development and barrier function assessment.

The ever-stricter regulations on animal experiments in the field of cosmetic testing have prompted a surge in skin-related research with a special focus on recapitulation of thein vivoskin structurein vitro. In vitrohuman skin models are seen as an important tool for skin research, which in recent years attracted a lot of attention and effort, with researchers moving from the simplest 2-layered models (dermis with epidermis) to models that incorporate other vital skin structures such as hypodermis, vascular structures, and skin appendages. In this study, we designed a microfluidic device with a reverse flange-shaped anchor that allows culturing of anin vitroskin model in a conventional 6-well plate and assessing its barrier function without transferring the skin model to another device or using additional contraptions. Perfusion of the skin model through vascular-like channels improved the morphogenesis of the epidermis compared with skin models cultured under static conditions. This also allowed us to assess the percutaneous penetration of the tested caffeine permeation and vascular absorption, which is one of the key metrics for systemic drug exposure evaluation.

Noninvasive evaluation of the skin barrier in reconstructed human epidermis using speckle analysis: Correlation with Raman microspectroscopy.

BACKGROUND: Reconstructed epidermis models, obtained from 3D keratinocytes culture, have gained significant prominence as prototypes for safety and efficacy testing in skin research. To effectively evaluate these models, it is essential to perform molecular and functional characterization. The skin's barrier function is one of the essential aspects of the epidermis that needs to be assessed. A noninvasive method is thus required for the evaluation of the skin barrier in these models. With this perspective, the aim of this feasibility study is to apply the speckle technique for the assessment of the skin barrier in the Reconstructed Human Epidermis (RHE). MATERIALS AND METHODS: Speckle analysis as well as Raman microspectroscopy were performed on RHE samples at two maturation days, D17 and D20. RESULTS: Between D17 and D20, our study showed an increase in various Raman parameters, including stratum corneum percentage, lateral lipid packing, lipid-to-protein ratio, and protein secondary structure. Furthermore, the degree of light polarization and the speckle grain size also increased over this period. CONCLUSION: The speckle technique proved to be effective for evaluating the skin barrier in Reconstructed Human Epidermis (RHE) models. Comparison with Raman validates this approach and provides comprehensive molecular and functional characterization of reconstructive skin models.

Dermal stiffness governs the topography of the epidermis and the underlying basement membrane in young and old human skin.

The epidermis is a stratified epithelium that forms the outer layer of the skin. It is composed primarily of keratinocytes and is constantly renewed by the proliferation of stem cells and their progeny that undergo terminal differentiation as they leave the basal layer and migrate to the skin surface. Basal keratinocytes rest on a basement membrane composed of an extracellular matrix that controls their fate via integrin-mediated focal adhesions and hemidesmosomes which are critical elements of the epidermal barrier and promote its regenerative capabilities. The distribution of basal cells with optimal activity provides the basement membrane with its characteristic undulating shape; this configuration disappears with age, leading to epidermal weakness. In this study, we present an in-depth imaging analysis of basal keratinocyte anchorage in samples of human skin from participants across the age spectrum. Our findings reveal that skin aging is associated with the depletion of hemidesmosomes that provide crucial support for stem cell maintenance; their depletion correlates with the loss of the characteristic basement membrane structure. Atomic force microscopy studies of skin and in vitro experiments revealed that the increase in tissue stiffness observed with aging triggers mechanical signals that alter the basement membrane structure and reduce the extent of basal keratinocyte anchorage, forcing them to differentiate. Genomic analysis revealed that epidermal aging was associated with mechanical induction of the transcription factor Krüppel-like factor 4. The altered mechanical properties of tissue being a new hallmark of aging, our work opens new avenues for the development of skin rejuvenation strategies.

TCR signaling and cellular metabolism regulate the capacity of murine epidermal γδ T cells to rapidly produce IL-13 but not IFN-γ.

Resident epidermal T cells of murine skin, called dendritic epidermal T cells (DETCs), express an invariant γδ TCR that recognizes an unidentified self-ligand expressed on epidermal keratinocytes. Although their fetal thymic precursors are preprogrammed to produce IFN-γ, DETCs in the adult epidermis rapidly produce IL-13 but not IFN-γ early after activation. Here, we show that preprogrammed IFN-γ-producing DETC precursors differentiate into rapid IL-13 producers in the perinatal epidermis. The addition of various inhibitors of signaling pathways downstream of TCR to the in vitro differentiation model of neonatal DETCs revealed that TCR signaling through the p38 MAPK pathway is essential for the functional differentiation of neonatal DETCs. Constitutive TCR signaling at steady state was also shown to be needed for the maintenance of the rapid IL-13-producing capacity of adult DETCs because in vivo treatment with the p38 MAPK inhibitor decreased adult DETCs with the rapid IL-13-producing capacity. Adult DETCs under steady-state conditions had lower glycolytic capacity than proliferating neonatal DETCs. TCR stimulation of adult DETCs induced high glycolytic capacity and IFN-γ production during the late phase of activation. Inhibition of glycolysis decreased IFN-γ but not IL-13 production by adult DETCs during the late phase of activation. These results demonstrate that TCR signaling promotes the differentiation of IL-13-producing DETCs in the perinatal epidermis and is needed for maintaining the rapid IL-13-producing capacity of adult DETCs. The low glycolytic capacity of adult DETCs at steady state also regulates the rapid IL-13 response and delayed IFN-γ production after activation.

Radiation Dermatitis: Radiation-Induced Effects on the Structural and Immunological Barrier Function of the Epidermis.

An important hallmark of radiation dermatitis is the impairment of the mitotic ability of the stem/progenitor cells in the basal cell layers due to radiation-induced DNA damage, leading to suppressed cell renewal in the epidermis. However, this mechanism alone does not adequately explain the complex pathogenesis of radiation-induced skin injury. In this review, we summarize the latest findings on the complex pathogenesis of radiation dermatitis and correlate these with the clinical features of radiation-induced skin reactions. The current studies show that skin exposure to ionizing radiation induces cellular senescence in the epidermal keratinocytes. As part of their epithelial stress response, these senescent keratinocytes secrete pro-inflammatory mediators, thereby triggering skin inflammation. Keratinocyte-derived cytokines and chemokines modulate intercellular communication with the immune cells, activating skin-resident and recruiting skin-infiltrating immune cells within the epidermis and dermis, thereby orchestrating the inflammatory response to radiation-induced tissue damage. The increased expression of specific chemoattractant chemokines leads to increased recruitment of neutrophils into the irradiated skin, where they release cytotoxic granules that are responsible for the exacerbation of an inflammatory state. Moreover, the importance of IL-17-expressing γδ-T cells to the radiation-induced hyperproliferation of keratinocytes was demonstrated, leading to reactive hyperplasia of the epidermis. Radiation-induced, reactive hyperproliferation of the keratinocytes disturbs the fine-tuned keratinization and cornification processes, leading to structural dysfunction of the epidermal barrier. In summary, in response to ionizing radiation, epidermal keratinocytes have important structural and immunoregulatory barrier functions in the skin, coordinating interacting immune responses to eliminate radiation-induced damage and to initiate the healing process.

In vitro generation of epidermal keratinocytes from human CD34-positive hematopoietic stem cells.

The epidermis is largely composed of keratinocytes (KCs), and the proliferation and differentiation of KCs from the stratum basale to the stratum corneum is the cellular hierarchy present in the epidermis. In this study, we explore the differentiation abilities of human hematopoietic stem cells (HSCs) into KCs. Cultured HSCs positive for CD34, CD45, and CD133 with prominent telomerase activity were induced with keratinocyte differentiation medium (KDM), which is composed of bovine pituitary extract (BPE), epidermal growth factor (EGF), insulin, hydrocortisone, epinephrine, transferrin, calcium chloride (CaCl2), bone morphogenetic protein 4 (BMP4), and retinoic acid (RA). Differentiation was monitored through the expression of cytokeratin markers K5 (keratin 5), K14 (keratin 14), K10 (keratin 10), K1 (keratin 1), transglutaminase 1 (TGM1), involucrin (IVL), and filaggrin (FLG) on day 0 (D0), day 6 (D6), day 11 (D11), day 18 (D18), day 24 (D24), and day 30 (D30) using immunocytochemistry, fluorescence microscopy, flow cytometry, qPCR, and Western blotting. The results revealed the expression of K5 and K14 genes in D6 cells (early keratinocytes), K10 and K1 genes in D11-D18 cells (mature keratinocytes) with active telomerase enzyme, and FLG, IVL, and TGM1 in D18-D24 cells (terminal keratinocytes), and by D30, the KCs were completely enucleated similar to cornified matrix. This method of differentiation of HSCs to KCs explains the cellular order exists in the normal epidermis and opens the possibility of exploring the use of human HSCs in the epidermal differentiation.

Penetration rates into the stratum corneum layer: A novel quantitative indicator for assessing skin barrier function.

BACKGROUND: The stratum corneum (SC), the outermost layer of the skin epidermis, acts as an effective bi-directional barrier, preventing water loss (inside-outside barrier) and entry of foreign substances (outside-inside barrier). Although transepidermal water loss (TEWL) is a widely-used measure of barrier function, it represents only inside-outside protection. Therefore, we aimed to establish a non-invasive method for quantitative evaluation of the outside-inside barrier function and visually present a skin barrier model. MATERIALS AND METHODS: Skin barrier damage was induced by applying a closed patch of 1% sodium dodecyl sulfate to the forearms of eight participants; they were instructed to apply a barrier cream on a designated damaged area twice daily for 5 days. The SC barrier was evaluated by measuring TEWL and fluorescein sodium salt penetration rate before, immediately after, and 5 days after damage. The penetration rate was assessed using tape-stripping (TS) technique and fluorescence microscopy. RESULTS: The rates of fluorescein sodium salt penetration into the lower layers of SC differed significantly based on the degree of skin barrier damage. The correlation between penetration rate and TEWL was weak after two rounds of TS and became stronger after subsequent rounds. Five days after skin barrier damage, the penetration rate of all layers differed significantly between areas with and without the barrier cream application. CONCLUSION: Our findings demonstrated that the penetration rate was dependent on skin barrier conditions. The penetration rate and corresponding fluorescence images are suitable quantitative indicators that can visually represent skin barrier conditions.

Epidermal loss of Bcl6 exacerbates MC903-induced atopic dermatitis-like skin inflammation.

Atopic dermatitis (AD) is a chronic inflammatory skin disease where Th2-type immune responses are dominant. In the lesional skin of AD, keratinocytes show differentiation defects and secrete proinflammatory cytokines and chemokines, amplifying Th2-type responses in AD. We previously reported that inducible loss of B-cell lymphoma 6 (Bcl6), a transcription repressor and a master transcriptional regulator of follicular helper T cells and germinal center B cells, in the whole body results in upregulation of Th2-related cytokines in mouse skin. However, the role of Bcl6 in keratinocytes remains to be clarified. Here, we observed that BCL6 positively regulates the expression of keratinocyte differentiation markers and plasma membrane localization of adherence junctional proteins in keratinocyte cell culture. Although keratinocyte-specific loss of Bcl6 alone did not induce AD-like skin inflammation, it aggravates MC903-induced AD-like skin inflammation in mice. In addition, Bcl6 expression is decreased in the epidermis of lesional skin from MC903-induced AD-like skin inflammation in mice. These results strongly suggest that Bcl6 downregulation in keratinocytes contributes to the development and aggravation of AD-like skin inflammation in mice.

NECTIN4-targeted antibody-drug conjugate is a potential therapeutic option for extramammary Paget disease.

Extramammary Paget disease (EMPD) is a rare skin cancer mainly found in areas rich in apocrine sweat glands. Since the effective treatments for advanced and/or metastasized EMPD are limited, there is an urgent need to develop novel therapeutic approaches. Nectin cell adhesion molecule 4 (NECTIN4) is highly expressed in cancers and considered to be a promising therapeutic target. NECTIN4 is also expressed in EMPD, but its role and the efficacy of NECTIN4-targeted therapy in EMPD remain unclear. This study investigated the potential of NECTIN4 as a novel therapeutic target for EMPD. NECTIN4 expression was immunohistochemically analysed in EMPD patients' primary (118 samples) and metastatic (21 samples) lesions. Using an EMPD cell line, KS-EMPD-1, the effects of NECTIN4 inhibition on cell proliferation and migration were investigated. NECTIN4 was expressed in primary and metastatic EMPD lesions, and the H-score of NECTIN4 staining was significantly higher in metastatic lesions than in primary ones. Knockdown of NECTIN4 significantly inhibited cell proliferation and affected cell migration. The cytotoxic effects of NECTIN4-targeted antibody-drug conjugate (ADC) were further evaluated, revealing a significant decrease in EMPD cell viability. In conclusion, NECTIN4 is a potential therapeutic target and NECTIN4-targeted ADC is promising as a therapeutic option for EMPD.

Epidermal growth factor receptor inhibition leads to cellular phenotype correction of DSP-mutated keratinocytes.

Desmoplakin (DSP) is a desmosomal component expressed in skin and heart, essential for desmosome stability and intermediate filament connection. Pathogenic variants in the DSP gene encoding DSP, lead to heterogeneous skin, adnexa and heart-related phenotypes, including skin fragility, woolly hair (WH), palmoplantar keratoderma (PPK) and arrhythmogenic/dilated cardiomyopathy (ACM/DCM). The ambiguity of computer-based prediction analysis of pathogenicity and effect of DSP variants, indicates a necessity for functional analysis. Here, we report a heterozygous DSP variant that was not previously described, NM_004415.4:c.3337C>T (NM_004415.4(NP_004406.2):p.(Arg1113*)) in a patient with PPK, WH and ACM. RNA and protein analysis revealed ~50% reduction of DSP mRNA and protein expression. Patient's keratinocytes showed fragile cell-cell connections and perinuclear retracted intermediate filaments. Epidermal growth factor receptor (EGFR) is a transmembrane protein expressed in the basal epidermal layer involved in proliferation and differentiation, processes that are disrupted in the development of PPK, and in the regulation of the desmosome. In skin of the abovementioned patient, evident EGFR upregulation was observed. EGFR inhibition in patient's keratinocytes strongly increased DSP expression at the plasma membrane, improved intermediate filament connection with the membrane edges and reduced the cell-cell fragility. This cell phenotypic recovery was due to a translocation of DSP to the plasma membrane together with an increased number of desmosomes. These results indicate a therapeutic potential of EGFR inhibitors for disorders caused by DSP haploinsufficiency.

Lipids in the American Alligator stratum corneum provide insights into the evolution of vertebrate skin.

In terrestrial vertebrates, the outermost layer of the skin, the stratum corneum (SC), provides a durable and flexible interface with the environment and is comprised of corneocytes embedded in lipids. However, the morphology and lipid composition of the SC varies throughout evolutionary history. Because crocodilians and birds phylogenetically bracket the Archosaurian clade, lipid composition in crocodilian SC may be compared with that of birds and other vertebrates to make inferences about broader phylogenetic patterns within Archosaurs while highlighting adaptations in vertebrate skin. We identified and quantified lipid classes in the SC of the American Alligator (Alligator mississippiensis) from three skin regions varying in mobility. Our results find similarities in lipid composition between alligator and avian SC, including a high percentage of cerebrosides, a polar lipid previously found only in the SC of birds and bats. Furthermore, polar lipids were more abundant in the most mobile region of the SC. Because polar lipids bind with water to increase skin hydration and therefore its pliability under physical stress, we hypothesize that selection for lipids in Archosaurian SC was driven by the unique distribution of proteins in the SC of this clade, and cerebrosides may have served as pre-adaptations for flight.

Higher Expression of Lympho-epithelial Kazal-type-Related Inhibitor-1 Fragments and Decreased Desquamation in the Lesional Skin of Nummular Eczema.

Nummular eczema, a chronic dermatitis characterized by coin-shaped lesions, was first documented in 1857. However, its pathophysiological characteristics are still not well known. To investigate differences in the regulation of the desquamation process in the stratum corneum of lesional and nonlesional skin of patients with nummular eczema and healthy control subjects, tape-stripped stratum corneum samples from patients with nummular eczema and healthy volunteers were analysed using immunofluorescence staining and western blot analysis. In the nummular eczema lesional skin, expression of desmoglein-1, desmocollin-1, and corneodesmosin exhibited a disorganized, dense or partially diffuse non-peripheral pattern with increased intensity, compared with the peripheral patterns observed in healthy or nonlesional skin, suggesting the impaired desquamation process in nummular eczema. Furthermore, although the expression of the desquamation-related serine proteases, kallikrein-related peptidase 7 and 5, was increased in nummular eczema lesional skin, the immunofluorescence staining of lympho-epithelial Kazal-type-related inhibitor-1, an endogenous inhibitor of various kallikrein-related peptidases, and its fragments were significantly increased in the nummular eczema lesional skin, suggesting its contribution to the inhibition of corneodesmosomal degradation. Therefore, the increased detection of corneodesmosomal proteins in nummular eczema lesions may be due to the increased amount of the fragments of lympho-epithelial Kazal-type-related inhibitor-1, which could contribute to delayed desquamation.

A novel three-dimensional Nrf2 reporter epidermis model for skin sensitization assessment.

Skin sensitization assessment has progressed from the use of animal models towards the application of New Approach Methodologies (NAMs). Several skin sensitization NAMs are accepted for regulatory use, but a majority relies on submerged in vitro cell cultures that limit their applicability domain, posing challenges for testing hydrophobic chemicals and mixtures. A newly developed three-dimensional (3D) Nrf2 reporter epidermis model for skin sensitization assessment is reported. This NAM may help to overcome these limitations. The NAM combines the in vivo-like biology and exposure conditions of 3D epidermis models with the reliability, convenience, and cost-effectiveness of secreted reporter gene technology. The Keap1-Nrf2-ARE pathway was chosen as the reporter gene read-out, as it is induced by most skin sensitizers and already adopted in OECD Test guideline 442D. Immortalized human primary keratinocytes (Ker-CT) were stably transfected with the pIGB-Nrf2-SEAP vector to construct a Nrf2 reporter cell line. Ker-CT Nrf2 reporter cells showed negligible basal expression of the Secreted Embryonic Alkaline Phosphatase (SEAP) reporter, which was induced 13.5-fold by exposure to the skin sensitizer cinnamic aldehyde (CA). Co-exposure to CA and the Nrf2 inhibitor glucocorticoid clobetasol propionate significantly suppressed the CA-induced SEAP expression, confirming dependance of the SEAP expression on Nrf2 activation. Using air-liquid interface and animal constituent free culture conditions, the Ker-CT Nrf2 reporter cells differentiated to stratified 3D epidermis models with an in vivo-like skin architecture and functional skin barrier. Evaluation of a Ker-CT Nrf2 reporter cell-based 2D assay by testing 10 conventional reference chemicals showed a predictive accuracy for skin sensitization potential of 80% and 70% compared to LLNA and human data in two independent laboratories and a high intra- and interlaboratory reproducibility. Moreover, the 3D epidermis models predicted 3 sensitizing and 2 non-sensitizing reference chemicals correctly in a first proof-of-concept study. Further investigations foresee the testing of additional chemicals, including hydrophobic compounds and mixtures to confirm the potential of the 3D epidermis models to broaden the applicability domain for NAM-based skin sensitization assessment.

Penetration of topically applied polymeric nanoparticles across the epidermis of thick skin from rat.

The barrier function of the epidermis poses a significant challenge to nanoparticle-mediated topical delivery. A key factor in this barrier function is the thickness of the stratum corneum (SC) layer within the epidermis, which varies across different anatomical sites. The epidermis from the palms and soles, for instance, have thicker SC compared to those from other areas. Previous studies have attempted to bypass the SC layer for nanoparticle penetration by using physical disruption; however, these studies have mostly focused on non-thick skin. In this study, we investigate the role of SC-disrupting mechano-physical strategies (tape-stripping and microneedle abrasion) on thick and thin skin, in allowing transdermal penetration of topically applied nanoparticles using an ex-vivo skin model from rat. Our findings show that tape-stripping reduced the overall thickness of SC in thick skin by 87%, from 67.4 ± 17.3µm to 8.2 ± 8.5µm, whereas it reduced thin skin SC by only 38%, from 9.9 ± 0.6µm to 6.2 ± 3.2µm. Compared to non-thick skin, SC disruption in thick skin resulted in higher nanoparticle diffusion. Tape-stripping effectively reduces SC thickness of thick skin and can be potentially utilized for enhanced penetration of topically applied nanoparticles in skin conditions that affect thick skin.

Epidermal ET-1 signal induces activation of resting hair follicles by upregulating the PI3K/AKT pathway in the dermis.

The prevalence of alopecia has increased recently. Hair loss is often accompanied by the resting phase of hair follicles (HFs). Dermal papilla (DP) plays a crucial role in HF development, growth, and regeneration. Activating DP can revive resting HFs. Augmenting WNT/ß-catenin signaling stimulates HF growth. However, the factors responsible for activating resting HFs effectively are unclear. In this study, we investigated epidermal cytokines that can activate resting HFs effectively. We overexpressed ß-catenin in both in vivo and in vitro models to observe its effects on resting HFs. Then, we screened potential epidermal cytokines from GEO DATASETs and assessed their functions using mice models and skin-derived precursors (SKPs). Finally, we explored the molecular mechanism underlying the action of the identified cytokine. The results showed that activation of WNT/ß-catenin in the epidermis prompted telogen-anagen transition. Keratinocytes infected with Ctnnb1-overexpressing lentivirus enhanced SKP expansion. Subsequently, we identified endothelin 1 (ET-1) expressed higher in hair-growing epidermis and induced the proliferation of DP cells and activates telogen-phase HFs in vivo. Moreover, ET-1 promotes the proliferation and stemness of SKPs. Western blot analysis and in vivo experiments revealed that ET-1 induces the transition from telogen-to-anagen phase by upregulating the PI3K/AKT pathway. These findings highlight the potential of ET-1 as a promising cytokine for HF activation and the treatment of hair loss.

Emerging Gene Therapeutics for Epidermolysis Bullosa under Development.

The monogenetic disease epidermolysis bullosa (EB) is characterised by the formation of extended blisters and lesions on the patient's skin upon minimal mechanical stress. Causal for this severe condition are genetic mutations in genes, leading to the functional impairment, reduction, or absence of the encoded protein within the skin's basement membrane zone connecting the epidermis to the underlying dermis. The major burden of affected families justifies the development of long-lasting and curative therapies operating at the genomic level. The landscape of causal therapies for EB is steadily expanding due to recent breakthroughs in the gene therapy field, providing promising outcomes for patients suffering from this severe disease. Currently, two gene therapeutic approaches show promise for EB. The clinically more advanced gene replacement strategy was successfully applied in severe EB forms, leading to a ground-breaking in vivo gene therapy product named beremagene geperpavec (B-VEC) recently approved from the US Food and Drug Administration (FDA). In addition, the continuous innovations in both designer nucleases and gene editing technologies enable the efficient and potentially safe repair of mutations in EB in a potentially permanent manner, inspiring researchers in the field to define and reach new milestones in the therapy of EB.

PNPLA1 knockdown inhibits esterification of γ-linolenic acid to ceramide 1 in differentiated keratinocytes.

Patatin-like phospholipase domain-containing 1 (PNPLA1) is crucial in the esterification of linoleic acid (LA; 18:2n-6) to ω-hydroxy fatty acids (FA) of ceramide 1 (Cer1), the major barrier lipid of the differentiated epidermis. We previously reported that γ-linolenic acid (GLA; 18:3n-6) as well as LA is esterified to Cer1 subspecies with sphingosine (d18:1) or eicosasphingosine (d20:1) amide-linked to two different ω-hydroxy FA (30wh:0; 32wh:1). Here, we further investigated whether PNPLA1 is also responsible for esterification of GLA to these Cer1 subspecies in normal human keratinocytes (NHK). As late/terminal differentiation was induced in NHK, PNPLA1 and differentiation markers were expressed, and LA-esterified Cer1 subspecies (18:2n-6/C30wh:0 or C32wh:0/d18:1; 18:2n-6/C32wh:0/d20:1) were detected, which were further increased with LA treatment. GLA-esterified Cer1 subspecies (18:3n-6/C30wh:0 or C32wh:0/d18:1; 18:3n-6/C32wh:0/d20:1) were detected only with GLA treatment. Specific small interfering RNA-mediated knockdown of PNPLA1 (KDP) in differentiated NHK decreased levels of these LA-esterified Cer1 subspecies overall and of involucrin (IVL), a terminal differentiation marker. Moreover, KDP resulted in lesser LA/GLA responses as characterized by more significant decreases in IVL and LA/GLA-esterified Cer1 subspecies overall and an accumulation of non-esterified ω-hydroxy ceramides, their putative precursors; the decrease of 18:3n-6/C32wh:0/d18:1, the predominant GLA-esterified Cer1 subspecies, specifically paralleled the increase of C32wh:0/d18:1, its corresponding precursor. PNPLA1 is responsible for NHK terminal differentiation and also for esterification of GLA to the ω-hydroxy FA of Cer1.

Increased tissue expression of IL-31 in patients with psoriasis.

Psoriasis is a chronic inflammatory skin disease, and its pathogenesis remains unclear. Although many studies have demonstrated the role of serum interleukin-31 (IL-31) in psoriasis, only one study has examined histopathological expression in lesional skin. This study aimed to investigate the expression of IL-31 in skin biopsy specimens of psoriasis patients compared to healthy subjects and identify its possible correlation to disease severity and itch intensity. Psoriasis patients and healthy volunteers were recruited. Four-millimeter punch biopsy was performed at the lesional skin of psoriasis patients and normal skin of healthy subjects. Expression of IL-31 was measured by immunohistochemistry. Baseline characteristics, disease activity, itch intensity, and related laboratory results were collected. Twenty-six biopsy specimens of psoriasis patients and 10 tissue samples of healthy subjects were evaluated. Epidermal and dermal psoriasis lesions had significantly higher IL-31 expression compared to the healthy skin (P < 0.001). However, there was no significant difference in lesional expression of IL-31 by disease severity or itch intensity. Increased IL-31 expression in the lesions of psoriasis patients suggests the involvement of IL-31 in the pathogenesis of psoriasis.