Development and homeostasis of the skin epidermis

Ultraviolet Light Causes Skin Cell Senescence: From Mechanism to Prevention Principle

The skin is an effective protective barrier that significantly protects the body from damage caused by external environmental factors. Furthermore, skin condition significantly affects external beauty. In today's era, which is of material and spiritual prosperity, there is growing attention on skincare and wellness. Ultraviolet radiation is one of the most common external factors that lead to conditions like sunburn, skin cancer, and skin aging. In this review, several mechanisms of UV-induced skin cell senescence are discussed, including DNA damage, oxidative stress, inflammatory response, and mitochondrial dysfunction, which have their own characteristics and mutual effects. As an illustration, mitochondrial dysfunction triggers electron evasion and the generation of more reactive oxygen species, leading to oxidative stress and the activation of the NLRP3 inflammasome, which in turn causes mitochondrial DNA (mt DNA) damage. Based on the current mechanism, suitable prevention and treatment strategies are proposed from sunscreen, dietary, and experimental medications respectively, aimed at slowing down skin cell aging and providing protection from ultraviolet radiation. The effects of ultraviolet rays on skin is summarized, offering insights and directions for future studies on mechanism of skin cell senescence, with an anticipation of discovering more effective prevention and cure methods.

Deciphering the links: Fragmented polystyrene as a driver of skin inflammation

Nano- and microplastics (NMPs), ubiquitous in the environment, pose significant health risks. We report for the first time a comprehensive study using in-vitro, in-vivo, and ex-vivo models to investigate the penetration and inflammatory effects of fragmented polystyrene (fPS) on human skin, including the analysis of both penetration depth and fPS amounts that penetrate the skin. Human keratinocyte (HaCaT) and human dermal fibroblast (HDF) cells exposed to fPS exhibited notable internalization and cytotoxicity. In a 3D human skin model, fPS particles penetrated the dermal layer within one hour, with an average maximum penetration of 4.7 μg for particles smaller than 2 µm. Similarly, mouse dorsal skin and human abdominal skin models confirmed fPS penetration. RNA sequencing revealed substantial upregulation of inflammatory genes, including IL-1α, IL-1β, IL-18, IL-6, IL-8, ICAM-1, FOS, and JUN, following fPS exposure. These findings were validated at both the mRNA and protein levels, indicating a robust inflammatory response. Notably, the inflammatory response in both the 3D human skin and mouse models increased in a dose-dependent manner, underscoring the toxicological impact of fPS on skin health. This study provides crucial insights into the mechanisms through which NMPs affect human health and underscores the need for further research to develop effective mitigation strategies.

Ontogeny of Skin Stem Cells and Molecular Underpinnings

Skin stem cells (SCs) play a pivotal role in supporting tissue homeostasis. Several types of SCs are responsible for maintaining and regenerating skin tissue. These include bulge SCs and others residing in the interfollicular epidermis, infundibulum, isthmus, sebaceous glands, and sweat glands. The emergence of skin SCs commences during embryogenesis, where multipotent SCs arise from various precursor populations. These early events set the foundation for the diverse pool of SCs that will reside in the adult skin, ready to respond to tissue repair and regeneration demands. A network of molecular cues regulates skin SC behavior, balancing quiescence, self-renewal, and differentiation. The disruption of this delicate equilibrium can lead to SC exhaustion, impaired wound healing, and pathological conditions such as skin cancer. The present review explores the intricate mechanisms governing the development, activation, and differentiation of skin SCs, shedding light on the molecular signaling pathways that drive their fate decisions and skin homeostasis. Unraveling the complexities of these molecular drivers not only enhances our fundamental knowledge of skin biology but also holds promise for developing novel strategies to modulate skin SC fate for regenerative medicine applications, ultimately benefiting patients with skin disorders and injuries.

Proteomics in Psoriasis: Recent Advances

Psoriasis continues to affect a large percentage of patients worldwide and strongly appears to be a systematic disease. Efforts are being made to understand its etiology, which have led to research extended to genomic analysis with a focus on the role of pro-inflammatory cytokines, which play a major role in the pathogenesis of the disease. Plasma proteomic analysis in various diseases has provided promising results for choosing the right treatment for psoriasis, suggesting that it could play a key role in the prevention, prognosis, and treatment of the disease by individualizing treatment choices based on the proteomic profile of each patient. In this review, we focus on existing data in the bibliography on proteomic analysis in psoriasis and relevant approaches to future targeted therapies.

The promising prospect of human hair follicle regeneration in the shadow of new tissue engineering strategies

Hair loss disorder (alopecia) affects numerous people around the world. The low effectiveness and numerous side effects of common treatments have prompted researchers to investigate alternative and effective solutions. Hair follicle (HF) bioengineering is the knowledge of using hair-inductive (trichogenic) cells. Most bioengineering-based approaches focus on regenerating folliculogenesis through manipulation of regulators of physical/molecular properties in the HF niche. Despite the high potential of cell therapy, no cell product has been produced for effective treatment in the field of hair regeneration. This problem shows the challenges in the functionality of cultured human hair cells. To achieve this goal, research and development of new and practical approaches, technologies and biomaterials are needed. Based on recent advances in the field, this review evaluates emerging HF bioengineering strategies and the future prospects for the field of tissue engineering and successful HF regeneration.

The GRHL3-regulated long non-coding RNA lnc-DC modulates keratinocytes differentiation by interacting with IGF2BP2 and up-regulating ZNF750

BACKGROUND

Aberrant keratinocytes differentiation has been demonstrated to be associated with a number of skin diseases. The roles of lncRNAs in keratinocytes differentiation remain to be largely unknown.

OBJECTIVE

Here we aim to investigate the role of lnc-DC in regulating epidermal keratinocytes differentiation.

METHODS

Expression of lnc-DC in the skin was queried in AnnoLnc and verified by FISH. The lncRNA expression profiles during keratinocytes differentiation were reanalyzed and verified by qPCR and FISH. Gene knock-down and over-expression were used to explore the role of lnc-DC in keratinocytes differentiation. The downstream target of lnc-DC was screened by whole transcriptome sequencing. CUT&RUN assay and siRNAs transfection was used to reveal the regulatory effect of GRHL3 on lnc-DC. The mechanism of lnc-DC regulating ZNF750 was revealed by RIP assay and RNA stability assay.

RESULTS

Lnc-DC was biasedly expressed in skin and up-regulated during epidermal keratinocytes differentiation. Knockdown lnc-DC repressed epidermal keratinocytes differentiation while over-express lnc-DC showed the opposite effect. GRHL3, a well-known transcription factor regulating keratinocytes differentiation, could bind to the promoter of lnc-DC and regulate its expression. By whole transcriptome sequencing, we identified that ZNF750 was a downstream target of lnc-DC during keratinocytes differentiation. Mechanistically, lnc-DC interacted with RNA binding protein IGF2BP2 to stabilize ZNF750 mRNA and up- regulated its downstream targets TINCR and KLF4.

CONCLUSION

Our study revealed the novel role of GRHL3/lnc-DC/ZNF750 axis in regulating epidermal keratinocytes differentiation, which may provide new therapeutic targets of aberrant keratinocytes differentiation related skin diseases.

Activating autophagy promotes skin regeneration induced by mechanical stretch during tissue expansion

Background

Tissue expansion, a technique in which skin regeneration is induced by mechanical stretch stimuli, is commonly used for tissue repair and reconstruction. In this study, we aimed to monitor the autophagy levels of expanded skin after the application of expansion stimuli and explore the effect of autophagy modulation on skin regeneration.

Methods

A rat scalp expansion model was established to provide a stable expanded skin response to mechanical stretch. Autophagy levels at different time points (6, 12, 24, 48 and 72 h after the last expansion) were detected via western blotting. The effect of autophagy regulation on skin regeneration during tissue expansion was evaluated via skin expansion efficiency assessment, western blotting, immunofluorescence staining, TUNEL staining and laser Doppler blood flow imaging.

Results

The autophagic flux reached its highest level 48 h after tissue expansion. Activating autophagy by rapamycin increased the area of expanded skin as well as the thicknesses of epidermis and dermis. Furthermore, activating autophagy accelerated skin regeneration during tissue expansion by enhancing the proliferation of cells and the number of epidermal basal and hair follicle stem cells, reducing apoptosis, improving angiogenesis, and promoting collagen synthesis and growth factor secretion. Conversely, the regenerative effects were reversed when autophagy was blocked.

Conclusions

Autophagy modulation may be a promising therapeutic strategy for improving the efficiency of tissue expansion and preventing the incidence of the complication of skin necrosis.

Can l-ascorbic acid and trans-resveratrol protect HaCaT cells from fine particulate matter toxicity?

Continuous exposure of human skin to air pollution can result in a range of undesirable skin conditions. In our recent study, UV and visible light were found to increase cytotoxicity of fine particulate matter (PM2.5 ) against human keratinocytes. Since it is impossible to avoid exposure of human skin to PM2.5 , effective strategies are needed to reduce their damaging effects. l-ascorbic acid and resveratrol were tested as potential topical agents against pollution-related skin impairment. Although these agents were previously found to ameliorate PM-dependent damage, the effect of light and seasonal variation of particles were not previously studied. EPR spin-trapping, DPPH assay, and singlet oxygen phosphorescence were used to determine the scavenging activities of the antioxidants. MTT, JC-10 and iodometric assays were used to analyze the effect on PM2.5 -induced cytotoxicity, mitochondrial damage and oxidation of lipids. Live-cell imaging was employed to examine wound-healing properties of cells. Light-induced, PM2.5 -mediated oxidative damage was examined by immunofluorescent staining. Both antioxidants effectively scavenged free radicals and singlet oxygen produced by PM2.5 , reduced cell death and prevented oxidative damage to HaCaT cells. l-ascorbic acid and resveratrol, especially when applied in combination, can protect HaCaT cells against the dark and light induced toxicity of PM2.5 .

Molecular and spatial landmarks of early mouse skin development

A wealth of specialized cell populations within the skin facilitates its hair-producing, protective, sensory, and thermoregulatory functions. How the vast cell-type diversity and tissue architecture develops is largely unexplored. Here, with single-cell transcriptomics, spatial cell-type assignment, and cell-lineage tracing, we deconstruct early embryonic mouse skin during the key transitions from seemingly uniform developmental precursor states to a multilayered, multilineage epithelium, and complex dermal identity. We identify the spatiotemporal emergence of hair-follicle-inducing, muscle-supportive, and fascia-forming fibroblasts. We also demonstrate the formation of the panniculus carnosus muscle (PCM), sprouting blood vessels without pericyte coverage, and the earliest residence of mast and dendritic immune cells in skin. Finally, we identify an unexpected epithelial heterogeneity within the early single-layered epidermis and a signaling-rich periderm layer. Overall, this cellular and molecular blueprint of early skin development-which can be explored at https://kasperlab.org/tools-establishes histological landmarks and highlights unprecedented dynamic interactions among skin cells.

Genetic and histological relationship between pheromone-secreting tissues of the musk gland and skin of juvenile Chinese forest musk deer (Moschus berezovskii Flerov, 1929)

BACKGROUND: The musk glands of adult male Chinese forest musk deer (Moschus berezovskii Flerov, 1929) (FMD), which are considered as special skin glands, secrete a mixture of sebum, lipids, and proteins into the musk pod. Together, these components form musk, which plays an important role in attracting females during the breeding season. However, the relationship between the musk glands and skin of Chinese FMD remains undiscovered. Here, the musk gland and skin of Chinese FMD were examined using histological analysis and RNA sequencing (RNA-seq), and the expression of key regulatory genes was evaluated to determine whether the musk gland is derived from the skin. METHODS: A comparative analysis of musk gland anatomy between juvenile and adult Chinese FMD was conducted. Then, based on the anatomical structure of the musk gland, skin tissues from the abdomen and back as well as musk gland tissues were obtained from three juvenile FMD. These tissues were used for RNA-seq, hematoxylin-eosin (HE) staining, immunohistochemistry (IHC), western blot (WB), and quantitative real-time polymerase chain reaction (qRT-PCR) experiments. RESULTS: Anatomical analysis showed that only adult male FMD had a complete glandular organ and musk pod, while juvenile FMD did not have any well-developed musk pods. Transcriptomic data revealed that 88.24% of genes were co-expressed in the skin and musk gland tissues. Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathway analysis found that the genes co-expressed in the abdomen skin, back skin, and musk gland were enriched in biological development, endocrine system, lipid metabolism, and other pathways. Gene Ontology (GO) enrichment analysis indicated that the genes expressed in these tissues were enriched in biological processes such as multicellular development and cell division. Moreover, the Metascape predictive analysis tool demonstrated that genes expressed in musk glands were skin tissue-specific. qRT-PCR and WB revealed that sex-determining region Y-box protein 9 (Sox9),Caveolin-1 (Cav-1), andandrogen receptor (AR) were expressed in all three tissues, although the expression levels differed among the tissues. According to the IHC results, Sox9 and AR were expressed in the nuclei of sebaceous gland, hair follicle, and musk gland cells, whereas Cav-1 was expressed in the cell membrane. CONCLUSIONS: The musk gland of Chinese FMD may be a derivative of skin tissue, and Sox9, Cav-1, and AR may play significant roles in musk gland development.

HAI-1 is required for the novel role of FGFBP1 in maintenance of cell morphology and F-actin rearrangement in human keratinocytes

Formation and maintenance of skin barrier function require tightly controlled membrane-associated proteolysis, in which the integral membrane Kunitz-type serine protease inhibitor, HAI-1, functions as the primary inhibitor of the membrane-associated serine proteases, matriptase and prostasin. Previously, HAI-1 loss in HaCaT human keratinocytes resulted in an expected increase in prostasin proteolysis but a paradoxical decrease in matriptase proteolysis. The paradoxical decrease in shed active matriptase is further investigated in this study with an unexpected discovery of novel functions of fibroblast growth factor-binding protein 1 (FGFBP1), which acts as an extracellular ligand that can rapidly elicit F-actin rearrangement and subsequently affect the morphology of human keratinocytes. This novel growth factor-like function is in stark contrast to the canonical activity of this protein through interactions with FGFs for its pathophysiological functions. This discovery began with the observation that HAI-1 KO HaCaT cells lose the characteristic cobblestone morphology of the parental cells and exhibit aberrant F-actin formation along with altered subcellular targeting of matriptase and HAI-2. The alterations in cell morphology and F-actin status caused by targeted HAI-1 deletion can be restored by treatment with conditioned medium from parental HaCaT cells, in which FGFBP1 was identified by tandem mass spectrometry. Recombinant FGFBP1 down to 1 ng/ml was able to revert the changes caused by HAI-1 loss. Our study reveals a novel function of FGFBP1 in the maintenance of keratinocyte morphology, which depends on HAI-1.

Water from Nitrodi’s Spring Induces Dermal Fibroblast and Keratinocyte Activation, Thus Promoting Wound Repair in the Skin: An In Vitro Study

The Romans knew of Nitrodi’s spring on the island of Ischia more than 2000 years ago. Although the health benefits attributed to Nitrodi’s water are numerous, the underlying mechanisms are still not understood. In this study, we aim to analyze the physicochemical properties and biological effects of Nitrodi’s water on human dermal fibroblasts to determine whether the water exerts in vitro effects that could be relevant to skin wound healing. The results obtained from the study indicate that Nitrodi’s water exerts strong promotional effects on dermal fibroblast viability and a significant stimulatory activity on cell migration. Nitrodi’s water induces alpha-SMA expression in dermal fibroblasts, thus promoting their transition to myofibroblast-protein ECM deposition. Furthermore, Nitrodi’s water reduces intracellular reactive oxygen species (ROS), which play an important role in human skin aging and dermal damage. Unsurprisingly, Nitrodi’s water has significant stimulatory effects on the cell proliferation of epidermal keratinocytes and inhibits the basal ROS production but enhances their response to the oxidative stress caused by external stimuli. Our results will contribute to the development of human clinical trials and further in vitro studies to identify inorganic and/or organic compounds responsible for pharmacological effects.

Induction of autophagy improves skin and hair conditions in dogs with underlying diseases

Background

Autophagy was reported to play a crucial role in maintaining general and skin health.

Methods

The study used a synthesized autophagy inducer (AI) (Aquatide™ cospharm Inc.; Daejeon, Korea), for evaluating the effects of autophagy on skin and hair in dogs. Twenty-two dogs with poor skin and hair which were diagnosed with canine atopic dermatitis (CAD) or pituitary-dependent hyperadrenocorticism (PDH) were included. Clinical scores using Canine Atopic Dermatitis Extent and Severity Index-04 (CADESI-04), Pruritus Visual Analog Scale (PVAS) and skin barrier function using measurement of transepidermal water loss (TEWL) were evaluated and canine keratinocytes were also used in vitro investigation of pro-inflammatory cytokines after AI treatment.

Results

In the AI group, clinical scores and skin barrier function were improved at week 8 significantly compared to in the other groups. In particular, the AI significantly improved the hair surface damage at 8 weeks compared to the baseline. In vitro, the AI reduced pro-inflammatory cytokines by activating the 78-kDa glucose-regulated protein (GRP78).

Conclusion

AI improve skin barrier function and hair damage and reduce pro-inflammatory cytokines by inhibiting reactive oxygen species (ROS) production in dogs.

A Novel Hair Restoration Technology Counteracts Androgenic Hair Loss and Promotes Hair Growth in A Blinded Clinical Trial

Androgenic alopecia (AGA) is a genetically predetermined condition that occurs as a result of stepwise miniaturization of the dermal papilla. During this process, the hair follicle suffers from increasing malnutrition and eventually dies, causing progressive hair loss. We recently highlighted that HIF-1α modulation may counteract hair loss. Here, we aim to demonstrate the positive influence of Tomorrowlabs HIF strengthening factor [HSF] hair restoration technology on hair biology in a monocentric blinded clinical trial over a total period of 9 months. A trial with 20 subjects (4 female and 16 male) and once-daily application of [HSF] hair restoration technology to the scalp was conducted. To assess the tolerability and efficacy of [HSF], testing included dermatological assessment, determination of hair loss by counting after combing, macro images of the head and TrichoScan evaluation of hair density as well as the proportion of anagen hair versus telogen hair. The clinical data show Tomorrowlabs [HSF] hair restoration to be safe and effective to counteract AGA. The use of Tomorrowlabs [HSF] hair restoration resulted in improvements in the clinical parameters of hair quality such as thickness (+7.2%), hair density (+14.3%) and shine and elasticity (+20.3%) during the test period. The effectiveness of the test product was further determined by a significant reduction in hair loss of an average of 66.8% in treatment-responsive subjects after 6 months and an increase in hair growth reaching up to 32.5%, with an average percentage change of 8.4% in all participants and 10.8% in the responsive patients (85% of the study cohort) after 9 months on TrichoScan evaluation. The hair growth cycle was harmonized with the result of an average anagen hair percentage increase of +8.0% and telogen hair percentage reduction of -14.0% shown in the test area. Applicable for both sexes in an alcohol-free formulation, beneficial to scalp health and free of complications or side effects, this novel product provides objectively measurable results counteracting hair loss paired with an improved look and feel of the hair.

Advances in Biodegradable Electronic Skin: Material Progress and Recent Applications in Sensing, Robotics, and Human-Machine Interfaces

The rapid growth of the electronics industry and proliferation of electronic materials and telecommunications technologies has led to the release of a massive amount of untreated electronic waste (e-waste) into the environment. Consequently, catastrophic environmental damage at the microbiome level and serious human health diseases threaten the natural fate of the planet. Currently, the demand for wearable electronics for applications in personalized medicine, electronic skins (e-skins), and health monitoring is substantial and growing. Therefore, "green" characteristics such as biodegradability, self-healing, and biocompatibility ensure the future application of wearable electronics and e-skins in biomedical engineering and bioanalytical sciences. Leveraging the biodegradability, sustainability, and biocompatibility of natural materials will dramatically influence the fabrication of environmentally friendly e-skins and wearable electronics. Here, the molecular and structural characteristics of biological skins and artificial e-skins are discussed. The focus then turns to the biodegradable materials, including natural and synthetic-polymer-based materials, and their recent applications in the development of biodegradable e-skin in wearable sensors, robotics, and human-machine interfaces (HMIs). Finally, the main challenges and outlook regarding the preparation and application of biodegradable e-skins are critically discussed in a near-future scenario, which is expected to lead to the next generation of biodegradable e-skins.

A reductionist approach to determine the effect of cell-cell contact on human epidermal stem cell differentiation

The balance between stem cell renewal and differentiation is determined by the interplay between intrinsic cellular controls and extrinsic factors presented by the microenvironment, or 'niche'. Previous studies on cultured human epidermis have utilised suspension culture and restricted cell spreading to investigate regulation of differentiation in single keratinocytes. However, keratinocytes are typically adherent to neighbouring cells in vivo. We therefore developed experimental models to investigate the combined effects of cell-ECM adhesion and cell-cell contact. We utilized lipid-modified oligonucleotides to form clusters of keratinocytes which were subsequently placed in suspension to induce terminal differentiation. In this experimental model cell-cell contact had no effect on suspension-induced differentiation of keratinocytes. We next developed a high-throughput platform for robust geometrical confinement of keratinocytes to hexagonal ECM-coated islands permitting direct cell-cell contact between single cells. As in the case of circular islands, differentiation was stimulated on the smallest single hexagonal islands. However, the percentage of involucrin-positive cells on small bowtie islands was significantly lower than on single islands, demonstrating that cell-cell contact reduced differentiation in response to decreased substrate adhesion. None of the small bowtie islands contained two involucrin-positive cells. Rather, if one cell was involucrin-positive the other was involucrin-negative. This suggests that there is intrinsic asymmetry in the effect of cell-cell contact in decreasing differentiation. Thus, our reductionist approaches provide new insights into the effect of the niche on keratinocyte differentiation. STATEMENT OF SIGNIFICANCE: Stem cell behaviour is regulated by a combination of external signals, including the nature of the adhesive substrate and cell-cell interactions. An understanding of how different signals are integrated creates the possibility of developing new biomaterials to promote tissue regeneration and broaden our understanding of skin diseases such as eczema and psoriasis, in which stem cell proliferation and differentiation are perturbed. In this study we have applied two methods to engineer intercellular adhesion of human epidermal stem cells, one involving lipid-modified DNA and the other involving hexagonal micropatterns. We show that the effect of cell-cell adhesion depends on cell-substrate adhesion and uncover evidence that two cells in equivalent environments can nevertheless behave differently.

ENKD1 promotes epidermal stratification by regulating spindle orientation in basal keratinocytes

Stratification of the epidermis is essential for the barrier function of the skin. However, the molecular mechanisms governing epidermal stratification are not fully understood. Herein, we demonstrate that enkurin domain-containing protein 1 (ENKD1) contributes to epidermal stratification by modulating the cell-division orientation of basal keratinocytes. The epidermis of Enkd1 knockout mice is thinner than that of wild-type mice due to reduced generation of suprabasal cells from basal keratinocytes through asymmetric division. Depletion of ENKD1 impairs proper orientation of the mitotic spindle and delays mitotic progression in cultured cells. Mechanistic investigation further reveals that ENKD1 is a novel microtubule-binding protein that promotes the stability of astral microtubules. Introduction of the microtubule-binding domain of ENKD1 can largely rescue the spindle orientation defects in ENKD1-depleted cells. These findings establish ENKD1 as a critical regulator of astral microtubule stability and spindle orientation that stimulates epidermal stratification in mammalian cells.

Towards standardized and reproducible research in skin microbiomes

Skin is a complex organ serving a critical role as a barrier and mediator of interactions between the human body and its environment. Recent studies have uncovered how resident microbial communities play a significant role in maintaining the normal healthy function of the skin and the immune system. In turn, numerous host-associated and environmental factors influence these communities' composition and diversity across the cutaneous surface. In addition, specific compositional changes in skin microbiota have also been connected to the development of several chronic diseases. The current era of microbiome research is characterized by its reliance on large data sets of nucleotide sequences produced with high-throughput sequencing of sample-extracted DNA. These approaches have yielded new insights into many previously uncharacterized microbial communities. Application of standardized practices in the study of skin microbial communities could help us understand their complex structures, functional capacities, and health associations and increase the reproducibility of the research. Here, we overview the current research in human skin microbiomes and outline challenges specific to their study. Furthermore, we provide perspectives on recent advances in methods, analytical tools and applications of skin microbiomes in medicine and forensics.

Human Basal and Suprabasal Keratinocytes Are Both Able to Generate and Maintain Dermo-Epidermal Skin Substitutes in Long-Term In Vivo Experiments

The basal layer of human interfollicular epidermis has been described to harbour both quiescent keratinocyte stem cells and a transit amplifying cell population that maintains the suprabasal epidermal layers. We performed immunofluorescence analyses and revealed that the main proliferative keratinocyte pool in vivo resides suprabasally. We isolated from the human epidermis two distinct cell populations, the basal and the suprabasal keratinocytes, according to the expression of integrin β4 (iβ4). We compared basal iβ4+ or suprabasal iβ4- keratinocytes with respect to their proliferation and colony-forming ability and their Raman spectral properties. In addition, we generated dermo-epidermal substitutes using freshly isolated and sorted basal iβ4+ or suprabasal iβ4- keratinocytes and transplanted them on immuno-compromised rats. We show that suprabasal iβ4- keratinocytes acquire a similar proliferative capacity as basal iβ4+ keratinocytes after two weeks of culture in vitro, with expression of high levels of iβ4 and downregulation of K10 expression. In addition, both basal iβ4+ and suprabasal iβ4- keratinocytes acquire authentic self-renewing properties during the in vitro 3D-culture phase and are able to generate and maintain a fully stratified epidermis for 16 weeks in vivo. Therefore, against the leading dogma, we propose that human suprabasal keratinocytes can retro-differentiate into true basal stem cells in a wound situation and/or when in contact with the basement membrane.

Transcriptional Basis of Psoriasis from Large Scale Gene Expression Studies: The Importance of Moving towards a Precision Medicine Approach

Transcriptome profiling techniques, such as microarrays and RNA sequencing (RNA-seq), are valuable tools for deciphering the regulatory network underlying psoriasis and have revealed large number of differentially expressed genes in lesional and non-lesional skin. Such approaches provide a more precise measurement of transcript levels and their isoforms than any other methods. Large cohort transcriptomic analyses have greatly improved our understanding of the physiological and molecular mechanisms underlying disease pathogenesis and progression. Here, we mostly review the findings of some important large scale psoriatic transcriptomic studies, and the benefits of such studies in elucidating potential therapeutic targets and biomarkers for psoriasis treatment. We also emphasised the importance of looking into the alternatively spliced RNA isoforms/transcripts in psoriasis, rather than focussing only on the gene-level annotation. The neutrophil and blood transcriptome signature in psoriasis is also briefly reviewed, as it provides the immune status information of patients and is a less invasive platform. The application of precision medicine in current management of psoriasis, by combining transcriptomic data, improves the clinical response outcome in individual patients. Drugs tailored to individual patient's genetic profile will greatly improve patient outcome and cost savings for the healthcare system.

Identification of key genes and signaling pathways related to Hetian sheep wool density by RNA-seq technology

Hetian sheep is a breed of sheep unique to the Hetian area of Xinjiang whose wool is used for producing blankets. Individual differences and hair follicle density are the key factors affecting wool production. Therefore, this study aimed to assess the Hetian sheep having different wool densities to statistically analyze the wool traits and hair follicle parameters. Furthermore, the transcriptome sequencing analysis was performed on the skins with different wool densities. The results showed that wool quantity and total hair follicle density of the high wool density sheep was significantly higher than low wool density sheep. The sheepskin with high wool density was found to grow more and finer wool than sheepskin with low wool density. A total of 1,452 differentially expressed genes were screened from the two sets of samples, including 754 upregulated and 698 downregulated genes. The differentially expressed genes were involved in the TGF-β/BMP and MAPK signaling pathways related to hair growth. Eleven differentially expressed genes belonging to the KAPs and KIFs might affect the fineness of the wool. The key genes, like the TNF, MAP2K2, INHBA, FST, PTPN11, MAP3K7, KIT, and BMPR1A, were found to probably affect the growth and density of the wool. The qPCR verified eight genes related to the MAPK pathway whose gene expression trends were consistent with the transcriptome sequencing results. This study furnishes valuable resources for enhancing the quality and production of wool in the Hetian sheep.

Delta/Jagged-mediated Notch signaling induces the differentiation of agr2-positive epidermal mucous cells in zebrafish embryos

Teleosts live in aquatic habitats, where they encounter ionic and acid-base fluctuations as well as infectious pathogens. To protect from these external challenges, the teleost epidermis is composed of living cells, including keratinocytes and ionocytes that maintain body fluid ionic homeostasis, and mucous cells that secret mucus. While ionocyte progenitors are known to be specified by Delta-Notch-mediated lateral inhibition during late gastrulation and early segmentation, it remains unclear how epidermal mucous cells (EMCs) are differentiated and maintained. Here, we show that Delta/Jagged-mediated activation of Notch signaling induces the differentiation of agr2-positive (agr2⁺) EMCs in zebrafish embryos during segmentation. We demonstrated that agr2⁺ EMCs contain cytoplasmic secretory granules and express muc5.1 and muc5.2. Reductions in agr2⁺ EMC number were observed in mib mutants and notch3 MOs-injected notch1a mutants, while increases in agr2⁺ cell number were detected in notch1a- and X-Su(H)/ANK-overexpressing embryos. Treatment with γ-secretase inhibitors further revealed that Notch signaling is required during bud to 15 hpf for the differentiation of agr2⁺ EMCs. Increased agr2⁺ EMC numbers were also observed in jag1a-, jag1b-, jag2a- and dlc-overexpressing, but not jag2b-overexpressing embryos. Meanwhile, reductions in agr2⁺ EMC numbers were detected in jag1a morphants, jag1b mutants, jag2a mutants and dlc morphants, but not jag2b mutants. Reduced numbers of pvalb8-positive epidermal cells were also observed in mib or jag2a mutants and jag1a or jag1b morphants, while increased pvalb8-positive epidermal cell numbers were detected in notch1a-overexpressing, but not dlc-overexpressing embryos. BrdU labeling further revealed that the agr2⁺ EMC population is maintained by proliferation. Cell lineage experiments showed that agr2⁺ EMCs are derived from the same ectodermal precursors as keratinocytes or ionocytes. Together, our results indicate that specification of agr2⁺ EMCs in zebrafish embryos is induced by DeltaC/Jagged-dependent activation of Notch1a/3 signaling, and the cell population is maintained by proliferation.

As aquatic organisms, fish must tolerate environmental challenges that include acid-base fluctuations and water-borne pathogens. The skin provides a first line of defense against these challenges, and specific cell types in the tissue are responsible for different protective functions. For example, keratinocytes provide body coverage, ionocytes are responsible for maintaining body fluid ionic homeostasis, and epidermal mucous cells generate a protective layer of mucus that covers the entire fish surface. In this study, we uncovered the developmental process in zebrafish that underlies the generation of epidermal mucous cells. First, we characterized epidermal mucous cells according to their expression of a particular gene, agr2. Then, we found that these cells differentiate soon after ionocytes and keratinocytes, and the molecular pathways that guide differentiation of all three cell types involve similar signals. While ionocytes and keratinocytes are known to be specified by Delta-Notch-mediated lateral inhibition, we found that epidermal mucous cells are specified by activation of Notch by Delta and Jagged ligands. Thus, our results suggest that the specification of these major cell types in the epidermis occurs via a streamlined Notch-dependent process. This utilization of temporally distinct signaling events can therefore generate diverse cell types in the fish epidermis.

Fine Particulate Matter-Induced Oxidative Stress Mediated by UVA-Visible Light Leads to Keratinocyte Damage

The human skin is exposed to various environmental factors including solar radiation and ambient air pollutants. Although, due to its physical and biological properties, the skin efficiently protects the body against the harm of environmental factors, their excessive levels and possible synergistic action may lead to harmful effects. Among particulate matter present in ambient air pollutants, PM2.5 is of particular importance for it can penetrate both disrupted and intact skin, causing adverse effects to skin tissue. Although certain components of PM2.5 can exhibit photochemical activity, only a limited amount of data regarding the interaction of PM2.5 with light and its effect on skin tissue are available. This study focused on light-induced toxicity in cultured human keratinocytes, which was mediated by PM2.5 obtained in different seasons. Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM) were employed to determine sizes of the particles. The ability of PM2.5 to photogenerate free radicals and singlet oxygen was studied using EPR spin-trapping and time-resolved singlet oxygen phosphorescence, respectively. Solar simulator with selected filters was used as light source for cell treatment to model environmental lightning conditions. Cytotoxicity of photoexcited PM2.5 was analyzed using MTT assay, PI staining and flow cytometry, and the apoptotic pathway was further examined using Caspase-3/7 assay and RT-PCR. Iodometric assay and JC-10 assay were used to investigate damage to cell lipids and mitochondria. Light-excited PM2.5 were found to generate free radicals and singlet oxygen in season-dependent manner. HaCaT cells containing PM2.5 and irradiated with UV-Vis exhibited oxidative stress features-increased peroxidation of intracellular lipids, decrease of mitochondrial membrane potential, enhanced expression of oxidative stress related genes and apoptotic cell death. The data indicate that sunlight can significantly increase PM2.5-mediated toxicity in skin cells.

Autocrine regulation of wound healing by ATP release and P2Y2 receptor activation

AIMS

Application of exogenous nucleotides can modulate wound healing via the activation of purinergic receptors. However, evidence for the release of endogenous nucleotides and the subsequent activation of purinergic receptors in this process has not been well defined. Therefore, the current study aimed to investigate wound-mediated nucleotide release and autocrine purinergic signalling during HaCaT keratinocyte wound closure following scratch injury.

MAIN METHODS

An in vitro scratch wound apparatus was employed to study wound healing over 24-h in the presence of modulators of ATP release, P2 receptors and pathways downstream of P2 receptor activation.

KEY FINDINGS

Adenosine 5'-triphosphate (ATP) was released from scratched cells. The ectonucleotidase apyrase and pharmacological inhibition of the nucleotide release hemichannel, pannexin-1, decreased wound closure over time. The non-selective P2Y receptor antagonist suramin and the selective P2Y₂ receptor antagonist AR-C118925XX, but not other P2 antagonists, decreased wound closure. AR-C118925XX decreased wound closure in a concentration-dependent fashion. However, exogenous P2Y₂ receptor agonists, ATP or uridine 5'-triphosphate, did not enhance wound closure. PCR and immunoblotting confirmed P2Y₂ receptor expression in HaCaT cells. U73122, a phospholipase C antagonist, and 2-aminoethoxydiphenylborate, an inositol 1,4,5-trisphosphate receptor-sensitive Ca²⁺-release channel antagonist, decreased wound closure consistent with P2Y₂ receptor activation. Absence of extracellular or intracellular Ca²⁺ or inhibition of intracellular Ca²⁺-release also impaired wound closure.

SIGNIFICANCE

These data describe a novel autocrine signalling mechanism in which wound-mediated release of endogenous ATP in response to mechanical scratching of HaCaT cells activates P2Y₂ receptors to facilitate wound closure.

Faces of cellular senescence in skin aging

The skin is comprised of different cell types with different proliferative capacities. Skin aging occurs with chronological age and upon exposure to extrinsic factors such as photodamage. During aging, senescent cells accumulate in different compartments of the human skin, leading to impaired skin physiology. Diverse skin cell types may respond differently to senescence-inducing stimuli and it is not clear how this results in aging-associated skin phenotypes and pathologies. This review aims to examine and provide an overview of current evidence of cellular senescence in the skin. We will focus on cellular characteristics and behaviour of different skin cell types undergoing senescence in the epidermis and dermis, with a particular focus on the complex interplay between mitochondrial dysfunction, autophagy and DNA damage pathways. We will also examine how the dermis and epidermis cope with the accumulation of DNA damage during aging.

Hallmarks of Aging in Macrophages: Consequences to Skin Inflammaging

The skin is our largest organ and the outermost protective barrier. Its aging reflects both intrinsic and extrinsic processes resulting from the constant insults it is exposed to. Aging in the skin is accompanied by specific epigenetic modifications, accumulation of senescent cells, reduced cellular proliferation/tissue renewal, altered extracellular matrix, and a proinflammatory environment favoring undesirable conditions, including disease onset. Macrophages (Mφ) are the most abundant immune cell type in the skin and comprise a group of heterogeneous and plastic cells that are key for skin homeostasis and host defense. However, they have also been implicated in orchestrating chronic inflammation during aging. Since Mφ are related to innate and adaptive immunity, it is possible that age-modified skin Mφ promote adaptive immunity exacerbation and exhaustion, favoring the emergence of proinflammatory pathologies, such as skin cancer. In this review, we will highlight recent findings pertaining to the effects of aging hallmarks over Mφ, supporting the recognition of such cell types as a driving force in skin inflammaging and age-related diseases. We will also present recent research targeting Mφ as potential therapeutic interventions in inflammatory skin disorders and cancer.

Culturing Keratinocytes on Biomimetic Substrates Facilitates Improved Epidermal Assembly In Vitro

Mechanotransduction is defined as the ability of cells to sense mechanical stimuli from their surroundings and translate them into biochemical signals. Epidermal keratinocytes respond to mechanical cues by altering their proliferation, migration, and differentiation. In vitro cell culture, however, utilises tissue culture plastic, which is significantly stiffer than the in vivo environment. Current epidermal models fail to consider the effects of culturing keratinocytes on plastic prior to setting up three-dimensional cultures, so the impact of this non-physiological exposure on epidermal assembly is largely overlooked. In this study, primary keratinocytes cultured on plastic were compared with those grown on 4, 8, and 50 kPa stiff biomimetic hydrogels that have similar mechanical properties to skin. Our data show that keratinocytes cultured on biomimetic hydrogels exhibited major changes in cellular architecture, cell density, nuclear biomechanics, and mechanoprotein expression, such as specific Linker of Nucleoskeleton and Cytoskeleton (LINC) complex constituents. Mechanical conditioning of keratinocytes on 50 kPa biomimetic hydrogels improved the thickness and organisation of 3D epidermal models. In summary, the current study demonstrates that the effects of extracellular mechanics on keratinocyte cell biology are significant and therefore should be harnessed in skin research to ensure the successful production of physiologically relevant skin models.

Regulation of Tissue Immune Responses by Local Glucocorticoids at Epithelial Barriers and Their Impact on Interorgan Crosstalk

The anti-inflammatory role of extra-adrenal glucocorticoid (GC) synthesis at epithelial barriers is of increasing interest with regard to the search for alternatives to synthetic corticosteroids in the therapy of inflammatory disorders. Despite being very effective in many situations the use of synthetic corticosteroids is often controversial, as exemplified in the treatment of influenza patients and only recently in the current COVID-19 pandemic. Exploring the regulatory capacity of locally produced GCs in balancing immune responses in barrier tissues and in pathogenic disorders that lead to symptoms in multiple organs, could provide new perspectives for drug development. Intestine, skin and lung represent the first contact zones between potentially harmful pathogens or substances and the body, and are therefore important sites of immunoregulatory mechanisms. Here, we review the role of locally produced GCs in the regulation of type 2 immune responses, like asthma, atopic dermatitis and ulcerative colitis, as well as type 1 and type 3 infectious, inflammatory and autoimmune diseases, like influenza infection, psoriasis and Crohn’s disease. In particular, we focus on the role of locally produced GCs in the interorgan communication, referred to as gut-skin axis, gut-lung axis or lung-skin axis, all of which are interconnected in the pathogenic crosstalk atopic march.

Key changes in chromatin mark mammalian epidermal differentiation and ageing

Dynamic shifts in chromatin states occur during embryonic epidermal development to support diverse epigenetic pathways that regulate skin formation and differentiation. However, it is not known whether the epigenomes established during embryonic development are maintained into adulthood or how these epigenetic mechanisms may be altered upon physiological ageing of the tissue. Here, we systematically profiled the nuclear enrichment of five key histone modifications in young and aged mouse epidermis and identified distinct chromatin states that are tightly correlated with cellular differentiation, as well as chromatin alterations that accompanied epidermal ageing. Our data showed that histone modifications, which become differentially enriched in undifferentiated basal or differentiated suprabasal cells during embryonic development, retained their distinct cell-type specific enrichment patterns in both young and aged adult tissues. Specifically, high levels of H3K4me3, H4K20me1 and H4K16ac marked the proliferative basal cells, while differentiated suprabasal cells accumulated H3K27me3 and H4K20me3 heterochromatin with a concomitant deacetylation of H4K16. We further identified shifts in the chromatin in the aged basal epidermis, which exhibited markedly reduced levels of H4K16ac, absence of high H4K20me1 staining and increased cell-to-cell variability in total histone H3 and H4 content. Changes in the chromatin profiles in aged tissues paralleled the altered expression of their corresponding histone modifiers in the basal keratinocytes. These results thus reveal the key histone signatures of epidermal differentiation that are conserved from embryonic development to adult homoeostasis, and provide insights into the epigenetic pathways underlying physiological skin ageing.

Increase in primary cilia in the epidermis of patients with atopic dermatitis and psoriasis

Primary cilia influence cell activity, and thus have a unique role in maintaining cell proliferation and differentiation. In atopic dermatitis (AD) and psoriasis, areas of skin inflammation exhibit dysregulated keratinocyte homeostasis. The role of primary cilia in these conditions remains unclear. The objectives of this study is to elucidate the incidence of primary cilia in skin inflammation and the potential mechanism underlying the dysregulation of keratinocytes. Primary cilia were observed using immunofluorescence staining. Normal skin samples were compared with skin samples from patients with AD or psoriasis in terms of cilia numbers and length. The effect of cytokine stimulation on ciliogenesis in keratinocytes was analysed using a primary keratinocyte culture. IFT88, an important ciliary intraflagellar protein, was blocked in Th2 and Th17 cytokines-stimulated keratinocytes. These effects were analysed with quantitative polymerase chain reaction and Western blot. Significant increases in ciliated cells were observed in AD and psoriasis skin samples compared with normal skin samples. The stimulation of keratinocytes using Th2 and Th17 cytokines modulated the formation of primary cilia. The amount of IFT88 in the primary cilia associated with the phosphorylation of JNK, but not p38, in keratinocytes stimulated with interleukin-13, 17A and 22. An increase of ciliated cells in the epidermis may impair keratinocyte differentiation under stress conditions caused by inflammation in both AD and psoriasis patients.

HIF-1α Stimulators Function Equally to Leading Hair Loss Agents in Enhancing Dermal Papilla Growth

INTRODUCTION

Androgenic alopecia (AGA) occurs due to progressive miniaturization of the dermal papilla (DP). During this process the hair follicle loses nutrition over time and eventually dies, causing the hair to fall out. Recent evidence suggests that hypoxia-inducible factor-1a (HIF-1α) modulation may counteract hair loss. This study aims to evaluate the proliferation of dermal papilla cells (DPCs) under the influence of a selection of commercially available topical hair loss drugs, compared to HIF-1α-stimulating agents.

MATERIALS AND METHODS

Using the hanging drop method, DPCs self-organized into spheroid shape, mirroring the three-dimensional (3D) structure of the DP in vivo. DP analogs were treated with established substances against AGA (minoxidil and caffeine) compared to HIF-1α-stimulating agents (deferoxamine [DFO] and deferiprone [DFP]), at 10 mM doses. DP analogs were simultaneously stained with 5-bromo-2'-deoxyuridine (BrdU) to evaluate impact of drug compounds on DP daughter cell production. Concurrently, fluorescent microscopy visualization of migration of daughter cells after 48 h in culture was performed.

RESULTS

DPC proliferation within the spheroid structure was significantly enhanced by caffeine, minoxidil, and the HIF-1α-stimulating agent DFP when compared to control. Highest proliferation was seen in the DFP-treated DP analogs. Migration of peripheral DP daughter cells was highest in control and DFO groups.

CONCLUSION

Here we demonstrate a significantly enhanced proliferative activity for both established substances against AGA (minoxidil and caffeine) and the HIF-1α-stimulating agent DFP in a 3D DPC spheroid culture model with equal results for DFP and minoxidil. These favorable characteristics make such compounds potential water-soluble alternatives to minoxidil.

Effect of Konjac Glucomannan (KGM) on the Reconstitution of the Dermal Environment against UVB-Induced Condition

Skin layers serve as a barrier against unexpected critical changes in the body due to environmental factors. Excessive ultraviolet (UV) B exposure increases the levels of age-related factors, leading to senescent cells and damaged skin tissues. Widely used as a dietary supplement, konjac (Amorphophallus konjac) glucomannan (KGM) has shown skin regeneration potential in patch or sheet form with anti-inflammatory or immunosuppressive effects. However, the ability of KGM to reconstitute senescent/damaged skin following UV radiation has not been explored. Here, we demonstrate that KGM alleviates skin damage by increasing the proportion of young cell populations in UVB-exposed senescent human epidermal primary melanocytes. Young cell numbers increased depending on KGM dosage, but the senescent cells were not removed. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis showed that mRNA and protein levels of age- and pigmentation-related factors decreased in a manner dependent on the rate at which new cells were generated. Moreover, an analysis of mRNA and protein levels indicated that KGM facilitated youth by increasing cell proliferation in UVB-damaged human fibroblasts. Thus, KGM is a highly effective natural agent for maintaining skin homeostasis by promoting the reconstitution of the dermal environment against UVB-induced acute senescence or skin damage.

Selective Translation of Cell Fate Regulators Mediates Tolerance to Broad Oncogenic Stress

Human skin tolerates a surprisingly high burden of oncogenic lesions. Although adult epidermis can suppress the expansion of individual mutant clones, the mechanisms behind tolerance to oncogene activation across broader regions of tissue are unclear. Here, we uncover a dynamic translational mechanism that coordinates oncogenic HRAS-induced hyperproliferation with loss of progenitor self-renewal to restrain aberrant growth and tumorigenesis. We identify translation initiator eIF2B5 as a central co-regulator of HRAS proliferation and cell fate choice. By coupling in vivo ribosome profiling with genetic screening, we provide direct evidence that oncogene-induced loss of progenitor self-renewal is driven by eIF2B5-mediated translation of ubiquitination genes. Ubiquitin ligase FBXO32 specifically inhibits epidermal renewal without affecting overall proliferation, thus restraining HRAS-driven tumorigenesis while maintaining normal tissue growth. Thus, oncogene-driven translation is not necessarily inherently tumor promoting but instead can manage widespread oncogenic stress by steering progenitor fate to prolong normal tissue growth.

The First Genome Survey of the Antarctic Krill (Euphausia superba) Provides a Valuable Genetic Resource for Polar Biomedical Research

The world-famous Antarctic krill (Euphausia superba) plays a fundamental role in the Antarctic food chain. It resides in cold environments with the most abundant biomass to support the Antarctic ecology and fisheries. Here, we performed the first genome survey of the Antarctic krill, with genomic evidence for its estimated genome size of 42.1 gigabases (Gb). Such a large genome, however, is beyond our present capability to obtain a good assembly, although our sequencing data are a valuable genetic resource for subsequent polar biomedical research. We extracted 13 typical protein-coding gene sequences of the mitochondrial genome and analyzed simple sequence repeats (SSRs), which are useful for species identification and origin determination. Meanwhile, we conducted a high-throughput comparative identification of putative antimicrobial peptides (AMPs) and antihypertensive peptides (AHTPs) from whole-body transcriptomes of the Antarctic krill and its well-known counterpart, the whiteleg shrimp (Penaeus vannamei; resident in warm waters). Related data revealed that AMPs/AMP precursors and AHTPs were generally conserved, with interesting variations between the two crustacean species. In summary, as the first report of estimated genome size of the Antarctic krill, our present genome survey data provide a foundation for further biological research into this polar species. Our preliminary investigations on bioactive peptides will bring a new perspective for the in-depth development of novel marine drugs.

Dynamic shifts in chromatin states differentially mark the proliferative basal cells and terminally differentiated cells of the developing epidermis

Post-translational modifications on nucleosomal histones represent a key epigenetic regulatory mechanism to mediate the complex gene expression, DNA replication, and cell cycle changes that occur in embryonic cells undergoing lineage specification, maturation, and differentiation during development. Here, we investigated the dynamics of 13 key histone marks in epidermal cells at three distinct stages of embryonic skin development and identified significant changes that corresponded with the maturation of the proliferative basal epidermal cells and terminally differentiated cells in the stratified layers. In particular, H3K4me3 and H3K27ac were accumulated and became more prominent in the basal cells at later stages of epidermal development, while H3K27me3 was found to be low in the basal cells but highly enriched in the differentiated suprabasal cell types. Constitutive heterochromatin marked by H4K20me3 was also significantly elevated in differentiated epidermal cells at late gestation stages, which exhibited a concomitant loss of H4K16 acetylation. These differential chromatin profiles were established in the embryonic skin by gestation day 15 and further amplified at E18 and in postnatal skin. Our results reveal the dynamic chromatin states that occur as epidermal progenitor cells commit to the lineage and differentiate into the different cells of the stratified epidermis and provide insight to the underlying epigenetic pathways that support normal epidermal development and homoeostasis.

Lesional skin in vitiligo exhibits delayed in vivo reepithelialization compared to the nonlesional skin

Vitiligo, a common skin disorder, is characterized by the loss of functional melanocytes resulting in the depigmentation of skin. Previous studies have demonstrated molecular and architectural alterations in the epidermal keratinocytes upon loss of melanocytes. The physiological implications of these "altered" keratinocytes are yet not known. We investigated the wound healing efficiency of lesional vs nonlesional skin in 12 subjects with stable nonsegmental vitiligo using histological and ultrastructural evaluation of partial-thickness wounds. The wounds were examined 12 days postinjury, coinciding with the reepithelialization phase of healing marked primarily by keratinocyte migration and proliferation. This study demonstrated a significant difference in the reepithelialization potential between the lesional and nonlesional skin. While all 12 nonlesional wounds demonstrated considerable neoepidermis formation on the 12th day post wound, only four of the corresponding lesional samples showed comparable reepithelialization; the rest remaining in the inflammatory phase. Ultrastructural studies using transmission electron microscopy as well as immunohistochemical staining revealed a reduced number of desmosomes, shorter keratin tonofilaments and an increase in myofibroblast population in the dermis of lesional reepithelialized tissue compared to the nonlesional reepithelialized samples. This study implicates gross functional perturbations in the lesional skin during physiological wound healing in vitiligo, suggesting that the breakdown of keratinocyte-melanocyte network results in delayed wound repair kinetics in the lesional skin when compared to patient-matched nonlesional skin.

Discovery of increased epidermal DNAH10 expression after regeneration of dermis in a randomized with-in person trial - reflections on psoriatic inflammation

Because molecular memories of past inflammatory events can persist in epidermal cells, we evaluated the long-term epidermal protein expression landscapes after dermal regeneration and in psoriatic inflammation. We first characterized the effects of two dermal regeneration strategies on transplants of indicator split-thickness skin grafts (STSGs) in ten adult patients with deep burns covering more than 20% of their body surface area. After fascial excision, three adjacent areas within the wound were randomized to receive a permanent dermal matrix, a temporary granulation-tissue-inducing dressing or no dermal component as control. Control areas were covered with STSG immediately, and treated areas after two-weeks of dermis formation. Epidermis-dermis-targeted proteomics of one-year-follow-up samples were performed for protein expression profiling. Epidermal expression of axonemal dynein heavy chain 10 (DNAH10) was increased 20-fold in samples having had regenerating dermis vs control. Given the dermal inflammatory component found in our dermal regeneration samples as well as in early psoriatic lesions, we hypothesized that DNAH10 protein expression also would be affected in psoriatic skin samples. We discovered increased DNAH10 expression in inflammatory lesions when compared to unaffected skin. Our results associate DNAH10 expression with cell proliferation and inflammation as well as with the epidermal memory resulting from the previous regenerative signals of dermis. This study (ISRCTN14499986) was funded by the Finnish Ministry of Defense and by government subsidies for medical research.

The uropygial gland of the monk parakeet Myiopsitta monachus: Histology, morphogenesis, and evolution within Psittaciformes (Aves)

We describe the morphology, histology, and histochemical characteristics of the uropygial gland (UG) of the monk parakeet Myiopsitta monachus. The UG has a heart-shape external appearance and adenomers extensively branched with a convoluted path, covered by a stratified epithelium formed by different cellular strata and divided into three zones (based on the epithelial height and lumen width), a cylindrical papilla with an internal structure of delicate type and two excretory pores surrounded by a feather tuft. Histochemical and lectin-histochemical techniques performed showed positivity against PAS, AB pH 2.5, AB-PAS, and some lectines, likely related to the granivorous feeding habits. Also, we describe the morphogenesis of the UG of the monk parakeet, which appears at embryological stage 34 as a pair of ectodermal invaginations. Heterochronic events in the onset development of the UG when compared with other birds could be recognized. Finally, to examine the phylogenetic occurrence of the UG within the Psittaciformes and infer its evolutionary history, we mapped its presence/absence over a molecular phylogeny. The reconstruction of the characters states at ancestral nodes revealed that the presence of the UG was the plesiomorphic feature for Psittaciformes and its loss evolved independently more than once.

Y-27632 preserves epidermal integrity in a human skin organ-culture (hSOC) system by regulating AKT and ERK signaling pathways

BACKGROUND

The human skin organ culture (hSOC) developed a century ago has been widely used to study various aspects of human skin development, differentiation, function, disease as well as skin appendages biology, however, maintaining the integrity of epidermal structure in long-term culture, has remained a challenge.

OBJECTIVES

Here we tried to establish a culture system using supplemented William's E medium in the presence of a ROCK inhibitor Y-27632 to maintain epidermal architecture in the long-term hSOC and to investigate the underlying mechanisms.

METHODS

Human breast skins, cut into 5 mm × 5 mm pieces, were cultured in supplemented William's E medium in the presence of 30μM Y-27632. The cultured skin tissues were collected at different time points for analysis of epidermal cell proliferation and differentiation by real time qRT-PCR and immunofluorescence (IF) staining. The keratinocyte suspension assay and in vivo treatment of Y-27632 on mouse were also carried out to study that the regulation of Y-27632 on keratinocyte proliferation and differentiation.

RESULTS

We found Y-27632 not only enhanced both basal cell proliferation and expression of suprabasal cell differentiation markers, but also maintained the balance of keratinocyte proliferation and differentiation through activation of AKT pathways on one hand and inhibition of ERK pathways on the other hand. The AKT inhibitor MK-2206 blocked the epidermal preservation effect of Y-27632, while the MEK/ERK inhibitor U0126 enhanced the preservation of epidermal structure in the hSOC.

CONCLUSIONS

Y-227632 can maintain skin epidermal integrity through regulation of AKT and ERK activity in the hSOC.

Keratin 6, 16 and 17-Critical Barrier Alarmin Molecules in Skin Wounds and Psoriasis

Located at the skin surface, keratinocytes (KCs) are constantly exposed to external stimuli and are the first responders to invading pathogens and injury. Upon skin injury, activated KCs secrete an array of alarmin molecules, providing a rapid and specific innate immune response against danger signals. However, dysregulation of the innate immune response of KCs may lead to uncontrolled inflammation and psoriasis pathogenesis. Keratins (KRT) are the major structural intermediate filament proteins in KCs and are expressed in a highly specific pattern at different differentiation stages of KCs. While KRT14-KRT5 is restricted to basal proliferative KCs, and KRT10-KRT1 is restricted to suprabasal differentiated KCs in normal skin epidermis, the wound proximal KCs downregulate KRT10-K1 and upregulate KRT16/KRT17-KRT6 upon skin injury. Recent studies have recognized KRT6/16/17 as key early barrier alarmins and upregulation of these keratins alters proliferation, cell adhesion, migration and inflammatory features of KCs, contributing to hyperproliferation and innate immune activation of KCs in response to an epidermal barrier breach, followed by the autoimmune activation of T cells that drives psoriasis. Here, we have reviewed how keratins are dysregulated during skin injury, their roles in wound repairs and in initiating the innate immune system and the subsequent autoimmune amplification that arises in psoriasis.

Abalone Collagen Extracts Potentiate Stem Cell Properties of Human Epidermal Keratinocytes

Stem cell activities in human tissues are critical for tissue integrity and function. Maintaining keratinocyte stem cells (KSCs) stemness helps sustain healthy skin by supporting keratinocyte renewal, involving the formation of epidermal barriers. In this study, abalone collagen (AC) extracts with molecular weights of 3 kDa (AC 1) and 300 kDa (AC 2) were compared to the epidermal growth factor (EGF) for their effects on cell proliferation, cell migration (wound healing), spheroid formation, and the expression level of stem cell markers on human keratinocytes (HaCaT cells). Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell proliferation was quantified by ATP and DNA content analysis and Sulforhodamine B (SRB) assays. Cell migration assay was determined using the scratch wound healing test. Spheroid formation was evaluated and the expression level of stem cell markers was investigated by western blot analysis. The results showed that AC 1 at the concentration of 100 µg/mL could stimulate HaCaT cell proliferation, migration, spheroid formation, and the expression level of stem cell markers (keratin 19, β-catenin, ALDH1A1) compared to the control. In conclusion, a smaller molecular weight of abalone collagen extract exhibits a better effect on keratinocytes proliferation, migration, and stemness, which could be a potential active ingredient in cosmeceutical products.

DNA damage in aging, the stem cell perspective

DNA damage is one of the most consistent cellular process proposed to contribute to aging. The maintenance of genomic and epigenomic integrity is critical for proper function of cells and tissues throughout life, and this homeostasis is under constant strain from both extrinsic and intrinsic insults. Considering the relationship between lifespan and genotoxic burden, it is plausible that the longest-lived cellular populations would face an accumulation of DNA damage over time. Tissue-specific stem cells are multipotent populations residing in localized niches and are responsible for maintaining all lineages of their resident tissue/system throughout life. However, many of these stem cells are impacted by genotoxic stress. Several factors may dictate the specific stem cell population response to DNA damage, including the niche location, life history, and fate decisions after damage accrual. This leads to differential handling of DNA damage in different stem cell compartments. Given the importance of adult stem cells in preserving normal tissue function during an individual's lifetime, DNA damage sensitivity and accumulation in these compartments could have crucial implications for aging. Despite this, more support for direct functional effects driven by accumulated DNA damage in adult stem cell compartments is needed. This review will present current evidence for the accumulation and potential influence of DNA damage in adult tissue-specific stem cells and propose inquiry directions that could benefit individual healthspan.

Theaflavin-Enriched Fraction Stimulates Adipogenesis in Human Subcutaneous Fat Cells

Skin provides the first defense line against the environment while preserving physiological homeostasis. Subcutaneous tissues including fat depots that are important for maintaining skin structure and alleviating senescence are altered during aging. This study investigated whether theaflavin (TF) in green tea (GT) has skin rejuvenation effects. Specifically, we examined whether high ratio of TF contents can induce the subcutaneous adipogenesis supporting skin structure by modulating lipid metabolism. The co-fermented GT (CoF-GT) fraction containing a high level of TF was obtained by co-fermentation with garland chrysanthemum (Chrysanthemum coronarium) and the conventionally fermented GT (F-GT) fraction was also obtained. The effects of the CoF- or F-GT fractions on adipogenesis were assessed using primary human subcutaneous fat cells (hSCF). Adipogenesis was evaluated based on lipid droplet (LD) formation, as visualized by Oil Red O staining; by analyzing of adipogenesis-related factors by real-time quantitative polyperase chain reaction (RT-qPCR); and by measuring the concentration of adiponectin released into the culture medium by enzyme-linked immunosorbent assay. TF-enriched CoF-GT fraction did not adversely affect hSCF cell viability but induced their adipogenic differentiation, as evidenced by LD formation, upregulation of adipogenesis-related genes, and adiponectin secretion. TF and TF-enriched CoF-GT fraction promoted differentiation of hSCFs and can therefore be used as an ingredient in rejuvenating agents.

Psoriasis: Keratinocytes or Immune Cells - Which Is the Trigger?

BACKGROUND

Psoriasis is a common, chronic inflammatory skin disorder, which can significantly impact quality of life. Despite major breakthroughs in our understanding of the pathogenesis of psoriasis, the chronological order of the underlying mechanisms leading to the development of psoriatic plaques remains to be completely understood.

SUMMARY

Although psoriasis is classically perceived as a T-cell disease, it is now well recognized that T lymphocytes do not function in exclusivity. This theory is supported by evidence from transgenic murine models that develop marked psoriasiform disease. In addition, immune cells and cytokines regulate both early and late events involved in the pathogenesis of psoriasis. Key Messages: Psoriasis is a complex disease - a dynamic interplay between immune cells, keratinocytes, and various other skin-resident cells, such as endothelial and immune cells. The contribution of each cell type is crucial in the initiation and maintenance phases of psoriatic alterations.

Multi-tasking epidermal stem cells: Beyond epidermal maintenance

Over the past decade, multiple stem cell compartments have been identified within the epidermis. These stem cell pools have different transcriptional properties, proliferative modes and anatomical locations, and they maintain distinct epidermal compartments. The importance of this stem cell heterogeneity and compartmentalization has been understood as a key feature in epidermal homeostasis. However, recent studies have revealed that these heterogeneous stem cells themselves act as a niche for neighboring cells, thereby establishing spatially and temporally patterned epidermal-dermal functional units. These studies provide a new perspective for interpreting the biological significance of stem cell heterogeneity and compartmentalization beyond their role in epidermal maintenance.

Enhancement of Cutaneous Wound Healing by Dsg2 Augmentation of uPAR Secretion

In addition to playing a role in adhesion, desmoglein 2 (Dsg2) is an important regulator of growth and survival signaling pathways, cell proliferation, migration and invasion, and oncogenesis. Although low-level Dsg2 expression is observed in basal keratinocytes and is downregulated in nonhealing venous ulcers, overexpression has been observed in both melanomas and nonmelanoma malignancies. Here, we show that transgenic mice overexpressing Dsg2 in basal keratinocytes primed the activation of mitogenic pathways, but did not induce dramatic epidermal changes or susceptibility to chemical-induced tumor development. Interestingly, acceleration of full-thickness wound closure and increased wound-adjacent keratinocyte proliferation was observed in these mice. As epidermal cytokines and their receptors play critical roles in wound healing, Dsg2-induced secretome alterations were assessed with an antibody profiler array and revealed increased release and proteolytic processing of the urokinase-type plasminogen activator receptor. Dsg2 induced urokinase-type plasminogen activator receptor expression in the skin of transgenic compared with wild-type mice. Wounding further enhanced urokinase-type plasminogen activator receptor in both epidermis and dermis with a concomitant increase in the prohealing laminin-332, a major component of the basement membrane zone, in transgenic mice. This study demonstrates that Dsg2 induces epidermal activation of various signaling cascades and accelerates cutaneous wound healing, in part, through urokinase-type plasminogen activator receptor-related signaling cascades.