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.

Identification of bZIP Transcription Factors That Regulate the Development of Leaf Epidermal Cells in Arabidopsis thaliana by Single-Cell RNA Sequencing.

Epidermal cells are the main avenue for signal and material exchange between plants and the environment. Leaf epidermal cells primarily include pavement cells, guard cells, and trichome cells. The development and distribution of different epidermal cells are tightly regulated by a complex transcriptional regulatory network mediated by phytohormones, including jasmonic acid, and transcription factors. How the fate of leaf epidermal cells is determined, however, is still largely unknown due to the diversity of cell types and the complexity of their regulation. Here, we characterized the transcriptional profiles of epidermal cells in 3-day-old true leaves of Arabidopsis thaliana using single-cell RNA sequencing. We identified two genes encoding BASIC LEUCINE-ZIPPER (bZIP) transcription factors, namely bZIP25 and bZIP53, which are highly expressed in pavement cells and early-stage meristemoid cells. Densities of pavement cells and trichome cells were found to increase and decrease, respectively, in bzip25 and bzip53 mutants, compared with wild-type plants. This trend was more pronounced in the presence of jasmonic acid, suggesting that these transcription factors regulate the development of trichome cells and pavement cells in response to jasmonic acid.

Pathophysiological Roles of Ion Channels in Epidermal Cells, Immune Cells, and Sensory Neurons in Psoriasis.

Psoriasis is a chronic inflammatory skin disease characterized by the rapid abnormal growth of skin cells in the epidermis, driven by an overactive immune system. Consequently, a complex interplay among epidermal cells, immune cells, and sensory neurons contributes to the development and progression of psoriasis. In these cellular contexts, various ion channels, such as acetylcholine receptors, TRP channels, Ca2+ release-activated channels, chloride channels, and potassium channels, each serve specific functions to maintain the homeostasis of the skin. The dysregulation of ion channels plays a major role in the pathophysiology of psoriasis, affecting various aspects of epidermal cells, immune responses, and sensory neuron signaling. Impaired function of ion channels can lead to altered calcium signaling, inflammation, proliferation, and sensory signaling, all of which are central features of psoriasis. This overview summarizes the pathophysiological roles of ion channels in epidermal cells, immune cells, and sensory neurons during early and late psoriatic processes, thereby contributing to a deeper understanding of ion channel involvement in the interplay of psoriasis and making a crucial advance toward more precise and personalized approaches for psoriasis treatment.

Biofabrication of biomimetic undulating microtopography at the dermal-epidermal junction and its effects on the growth and differentiation of epidermal cells.

The undulating microtopography located at the junction of the dermis and epidermis of the native skin is called rete ridges (RRs), which plays an important role in enhancing keratinocyte function, improving skin structure and stability, and providing three-dimensional (3D) microenvironment for skin cells. Despite some progress in recent years, most currently designed and manufactured tissue-engineered skin models still cannot replicate the RRs, resulting in a lack of biological signals in the manufactured skin models. In this study, a composite manufacturing method including electrospinning, 3D printing, and functional coating was developed to produce the epidermal models with RRs. Polycaprolactone (PCL) nanofibers were firstly electrospun to mimic the extracellular matrix environment and be responsible for cell attachment. PCL microfibers were then printed onto top of the PCL nanofibers layer by 3D printing to quickly prepare undulating microtopography and finally the entire structures were dip-coated with gelatin hydrogel to form a functional coating layer. The morphology, chemical composition, and structural properties of the fabricated models were studied. The results proved that the multi-process composite fabricated models were suitable for skin tissue engineering. Live and dead staining, cell counting kit-8 (CCK-8) as well as histology (haematoxylin and eosin (HE) methodology) and immunofluorescence (primary and secondary antibodies combination assay) were used to investigate the viability, metabolic activity, and differentiation of skin cells forin vitroculturing.In vitroresults showed that each model had high cell viability, good proliferation, and the expression of differentiation marker. It was worth noting that the sizes of the RRs affected the cell growth status of the epidermal models. In addition, the unique undulation characteristics of the epidermal-dermal junction can be reproduced in the developed epidermal models. Overall, thesein vitrohuman epidermal models can provide valuable reference for skin transplantation, screening and safety evaluation of drugs and cosmetics.

Live tracking of basal stem cells of the epidermis during growth, homeostasis and injury response in zebrafish.

Basal stem cells of the epidermis continuously differentiate into keratinocytes and replenish themselves via self-renewal to maintain skin homeostasis. Numerous studies have attempted to reveal how basal cells undergo differentiation or self-renewal; however, this has been hampered by a lack of robust basal cell markers and analytical platforms that allow single-cell tracking. Here, we report that zebrafish integrin beta 4 is a useful marker for basal cell labelling, irrespective of the body region, stage and regenerative status. We employed Cre-loxP recombination in combination with live cell tracking of single basal clones in the caudal fin and investigated the embryonic origin and behaviour of basal cells during fish growth and homeostasis. Although most basal cells, including those in fins, became quiescent in the adult stage, genetic cell ablation showed that basal cells were reactivated to either self-renew or differentiate, depending on the injured cell type. Our study provides a simple and easy-to-use platform for quantitative in vivo imaging of basal stem cells at wider stages and under various conditions.

Upregulation of IDO gene expression reduces the immunogenicity of epidermal cells and strengthens the immune protection of epidermal cells during transplantation treatment of wounds.

BACKGROUND: Epidermal cell transplantation is a feasible treatment option for large wounds; however, sources of autologous epidermal cells are often limited. Allogeneic epidermal cells can be cultured conveniently; however, related immune rejection needs to be addressed. Herein, we hypothesized that the immunogenicity of epidermal cells with high indoleamine 2,3-dioxygenase (IDO) expression may be reduced by gene transfection. METHODS/RESULTS: To test this hypothesis, we obtained stable transfectants by transfecting epidermal stem cells with a lentiviral vector encoding the IDO gene and screening them for puromycin resistance (a marker for successful transfection). The phenotype tested using cell counting kit -8 and Transwell assays confirmed that IDO-transfected epidermal cells maintained their characteristics. Co-culture of IDO-transfected epidermal cells with allogeneic CD4+ T cells in vitro showed that the upregulation of IDO expression in epidermal cells inhibited the proliferation of CD4+ T cells (P < 0.001, P < 0.001, and P < 0.001, respectively) and promoted their apoptosis (P = 0.00028, P = 0.0006, and P = 0.00247, respectively) and transformation into functional regulatory T cells (Tregs) (P = 0.0051, P = 0.0132, and P = 0.0248, respectively) compared with Con, NC, and 1-MT groups. The increased proportion of Tregs may be related to the overexpression of IDO, which promoted the expression of transforming growth factor beta (TGF-ß) (P = 0.0001, P = 0.0013, and, P = 0.0009) and interleukin (IL) 10 (IL-10) (P = 0.0062, P = 0.0058, and P = 0.0119) while inhibited the expression of IL-2 (P = 0.0012, P = 0.0126, and P = 0.0066). We further verified these effects in vivo as transplanted IDO-transfected epidermal stem cells were effective in treating wounds in mice. On days 5 and 7, wounds treated with IDO cells healed faster than those in the other groups (day 5: P = 0.012 and P = 0.0136; day 7: P = 0.0242 and P = 0.0187, respectively), whereas this effect was significantly inhibited by 1-methyltryptophan (1-MT) (day 5: P = 0.0303; day 7: P = 0.0105). Immunofluorescence staining detected IDO and CD4+ Foxp3+ Tregs in the transplanted wounds, which may promote Foxp3+ Tregs in the wound tissue (day 5: P < 0.0001, P < 0.0001, and P < 0.0001; day 7: P < 0.0001, P < 0.0001, and P < 0.0001), respectively) and decrease CD4+ T cells (day 5: P < 0.0001, P < 0.0001, and P < 0.0001; day 7: P < 0.0001, P < 0.0001, and P < 0.0001). CONCLUSION: Our results suggest that the upregulation of IDO expression in epidermal stem cells can reduce their immunogenicity by promoting Tregs, thus inducing the immune protection of epidermal stem cells.

P75NTR regulates autophagy through the YAP-mTOR pathway to increase the proliferation of interfollicular epidermal cells and promote wound healing in diabetic mice.

Wound healing is delayed in diabetic patients. Increased autophagy and dysfunction of interfollicular epidermal (IFE) cells are closely associated with delayed healing of diabetic wounds. Autophagy plays an important role in all stages of wound healing, but its role in diabetic wound healing and the underlying molecular mechanisms are not clear. Here, we found that diabetic mice had delayed wound healing and increased autophagy in wounds compared with normal mice and that chloroquine, an inhibitor of autophagy, decreased the level of autophagy, improved the function of IFE cells, and accelerated wound healing in diabetic mice. Treatment of IFE cells with advanced glycosylation end products (AGEs) resulted in increased microtubule-associated protein chain (LC3) expression and decreased prostacyclin-62 (P62) expression, indicating increased autophagy in AGE-treated IFE cells. Moreover, P75NTR reduced autophagy in IFE cells in the presence of AGEs and significantly increased the proliferation of IFE cells. In addition, P75NTR participated in regulating autophagy in IFE cells and in wounds in diabetic mice through the YAP-mTOR signalling pathway, which increased the functional activity of the cells and the healing rate of wounds in diabetic mice. Thus, our study suggests that P75NTR protects IFE cells against AGEs by affecting autophagy and accelerating wound healing in diabetic mice, providing a basis for understanding the role of autophagy in diabetic wound healing.

Human filaggrin monomer does not seem to be a proteasome target.

Absence of a functional proteasome in the suprabasal layers of the epidermis is responsible for keratosis linearis with ichthyosis congenital and sclerosing keratoderma syndrome. Patient epidermis shows hypergranulosis associated with abnormally shaped keratohyalin granules and abnormal distribution of filaggrin in the Stratum granulosum and Stratum corneum. This suggests that the proteasome is involved in the degradation of filaggrin. To test this hypothesis, the proteasome proteolytic activity was inhibited in 3D reconstructed human epidermis (RHE) with the specific clasto-lactacystin ß-lactone inhibitor. Confirming the efficacy of inhibition, ubiquitinated proteins accumulated in treated RHEs as compared to controls. Levels of urocanic acid (UCA) and pyrrolidone carboxylic acid (PCA), the end products of filaggrin degradation, were reduced. However, neither filaggrin accumulation nor appearance of filaggrin-derived peptides were observed. On the contrary, the amount of filaggrin was shown to decrease, and a similar tendency was observed for profilaggrin, its precursor. Accumulation of small cytoplasmic vesicles associated with a significant increase in autophagy markers indicated activation of the autophagy process upon proteasome inhibition. Taken together, these results suggest that the perturbation of UCA and PCA production after proteasome inhibition was probably due to down-regulation of filaggrin expression rather than to blocking of filaggrin proteolysis.

Comparative analysis of foliar epidermal anatomical traits and their taxonomic relevance in Lilium pumilum, L. brownii, and L. davidi.

The anatomical traits of plant species are essential for taxonomic analyses and evolutionary evaluations. Clarifying the anatomical characteristics of the foliar epidermis in three distinct Lilium species L. pumilum Delile, L. brownii F.E.Br. ex Miellez and L. davidii Duch. ex Elwes were studied in this article. The objective is to assess the taxonomic relevance of these characteristics and their potential as indicators of species divergence within the genus Lilium. Plant samples were gathered in Gansu, China, from numerous populations of each species that represented a range of climatic and ecological factors. A microscopic analysis employing thin slices and peel mounts was done to assess the stomatal density and dimensions. Significant interpopulation differences in stomatal features were found in the results, offering potential opportunities for taxonomic discrimination. The species differ in qualitative and quantitative characters to differentiate the three species. The links between the observed anatomical characteristics and species classification within the Lilium genus were clarified for the three studied species. In the end, this research advances knowledge of Lilium taxonomy, aids in conservation efforts, and deepens awareness of the general patterns of plant variety. RESEARCH HIGHLIGHTS: Epidermal Traits Aid Taxonomy: Cell shape, arrangement, and structures aid Lilium Identification. Cuticle Reveals Taxonomic Clues: Thickness, composition, and structure inform classification. Micromorphology for Species ID: Cell shape, wax, and striations differentiate Lilium species.

Comparative microscopic investigations of leaf epidermis in four Ajuga species from Korea.

The genus Ajuga is widely distributed in temperate to subtropical regions, and four species are currently recognized in Korea (A. decumbens, A. multiflora, A. nipponensis, and A. spectabilis), but epidermal anatomical differences across these species have never been described. A comparative study of the leaf micromorphological characteristics of Korean Ajuga species was performed using light microscopy (LM) and scanning electron microscopy (SEM) to elucidate their taxonomic usefulness and to assess leaf micromorphological diversity. Considerable diversity in epidermal and stomatal anatomy was observed across Korean Ajuga species. Species had both hypostomatic or amphistomatic leaves, with anomocytic, anisocytic, diactyic, or actinocytic stomatal complexes. Guard cell length across species ranged from 17.66 ± 0.57 µm to 32.50 ± 2.38 µm and correlated with genome size. Abnormal stomata were frequently observed in three species (A. decumbens, A. multiflora, and A. nipponensis) but not in A. spectabilis. Three types of glandular trichomes were found: peltate in all species, short-stalked in all species, and long-stalked glandular trichomes in A. multiflora. Among the investigated leaf micromophological characters, trichome type, epidermal cell shape, and stomatal morphology were all taxonomically informative traits at a species level. RESEARCH HIGHLIGHTS: A comprehensive micromorphological description of the leaf surface is provided for Korean Ajuga species using scanning electron microscopic (SEM) and light microscopic (LM) analyses. The diverse range of stomatal development and the occurrence of polymorphic stomatal types are documented for the first time in Korean Ajuga species. The great diversity in stomatal and trichome morphology in Korean Ajuga species are taxonomically useful traits for species identification.

Cooperative actin filament nucleation by the Arp2/3 complex and formins maintains the homeostatic cortical array in Arabidopsis epidermal cells.

Precise control over how and where actin filaments are created leads to the construction of unique cytoskeletal arrays within a common cytoplasm. Actin filament nucleators are key players in this activity and include the conserved actin-related protein 2/3 (Arp2/3) complex as well as a large family of formins. In some eukaryotic cells, these nucleators compete for a common pool of actin monomers and loss of one favors the activity of the other. To test whether this mechanism is conserved, we combined the ability to image single filament dynamics in the homeostatic cortical actin array of living Arabidopsis (Arabidopsis thaliana) epidermal cells with genetic and/or small molecule inhibitor approaches to stably or acutely disrupt nucleator activity. We found that Arp2/3 mutants or acute CK-666 treatment markedly reduced the frequency of side-branched nucleation events as well as overall actin filament abundance. We also confirmed that plant formins contribute to side-branched filament nucleation in vivo. Surprisingly, simultaneous inhibition of both classes of nucleator increased overall actin filament abundance and enhanced the frequency of de novo nucleation events by an unknown mechanism. Collectively, our findings suggest that multiple actin nucleation mechanisms cooperate to generate and maintain the homeostatic cortical array of plant epidermal cells.

Occurrence, structure, and function of short cells in maize leaf epidermis.

Short cells are specialised epidermal cells of grasses and they include cork and silica cells. The time of occurrence, distribution, and number of short cells differ among plants or tissues of the same plant. The present study aimed to assess the occurrence, structure, and function of short cells in the epidermis of maize (Zea mays L.) leaves from cultivar "Zhengdan 958″ under field and potted experimental conditions. Results showed that short cells occurred synchronously in multiple maize leaves. Few short cells occurred at the base of the fifth leaf; most were found at the middle and base of the sixth leaf, and throughout the seventh leaf. The accumulation of K+ and H2O2 in cork cells changed periodically with stomatal opening and closure, which was consistent with the accumulation of K+ and H2O2 in subsidiary cells; whereas no accumulation was observed in silica cells. Moreover, photosynthetic parameters and stomatal aperture were significantly higher in leaves containing short cells than in those without them in the same parts of different leaves or in different leaves at the same leaf position. Accumulation of K+ and H2O2 in cork cells increased with increasing water stress. In conclusion, short cells not only improved leaf mechanical support and photosynthetic performance, and maize drought resistance, but they also participated in stomatal regulation.

LGN loss randomizes spindle orientation and accelerates tumorigenesis in PTEN-deficient epidermis.

Loss of cell polarity and disruption of tissue organization are key features of tumorigenesis that are intrinsically linked to spindle orientation. Epithelial tumors are often characterized by spindle orientation defects, but how these defects impact tumor formation driven by common oncogenic mutations is not fully understood. Here, we examine the role of spindle orientation in adult epidermis by deleting a key spindle regulator, LGN, in normal tissue and in a PTEN-deficient mouse model. We report that LGN deficiency in PTEN mutant epidermis leads to a threefold increase in the likelihood of developing tumors on the snout, and an over 10-fold increase in tumor burden. In this tissue, loss of LGN alone increases perpendicular and oblique divisions of epidermal basal cells, at the expense of a planar orientation of division. PTEN loss alone does not significantly affect spindle orientation in these cells, but the combined loss of PTEN and LGN fully randomizes basal spindle orientation. A subset of LGN- and PTEN-deficient animals have increased amounts of proliferative spinous cells, which may be associated with tumorigenesis. These results indicate that loss of LGN impacts spindle orientation and accelerates epidermal tumorigenesis in a PTEN-deficient mouse model.

Postnatal Expression of Kitl Affects Pigmentation of the Epidermis.

KITL signaling is important for melanocyte development in mammals; however, its function in the melanocyte stem cells in adult skin is not well-understood. In this study, we have generated genetically modified mice that express a Kitl transgene under the control of a doxycycline-inducible promoter to investigate the impact of its overexpression in embryo, young postnatal, and adult skin with intact hair follicles. We report that overexpression of KITL influences the proliferation and differentiation of melanocytes as well as the self-renewal capacity of resident melanocyte stem cells within the follicular niche. Notably, activation of Kit-KITL signaling induced the migration of melanocytes from hair follicles to the epidermis. In addition, we demonstrate that a single pulse of Kitl transgene expression in postnatal mice results in long-lasting effects on melanocyte stem cells and their differentiated progeny as pigmented skin cells that persist through adulthood. Our findings indicate that regulation of KITL signaling in melanocyte lineage is crucial for melanocyte stem cell homeostasis and melanocyte cell differentiation in postnatal and adult mice.

ΔNp63 Regulates Homeostasis, Stemness, and Suppression of Inflammation in the Adult Epidermis.

The p63 transcription factor is critical for epidermis formation in embryonic development, but its role in the adult epidermis is poorly understood. In this study, we show that acute genetic ablation of ΔNp63, the main p63 isoform, in adult epidermis disrupts keratinocyte proliferation and self-maintenance and, unexpectedly, triggers an inflammatory psoriasis-like condition. Mechanistically, single-cell RNA sequencing revealed the downregulation of cell cycle genes, upregulation of differentiation markers, and induction of several proinflammatory pathways in ΔNp63-ablated keratinocytes. Intriguingly, ΔNp63-ablated cells disappear by 3 weeks after ablation, at the expense of the remaining nonablated cells. This is not associated with active cell death and is likely due to reduced self-maintenance and enhanced differentiation. Indeed, in vivo wound healing, a physiological readout of the epidermal stem cell function, is severely impaired upon ΔNp63 ablation. We found that the Wnt signaling pathway (Wnt10A, Fzd6, Fzd10) and the activator protein 1 (JunB, Fos, FosB) factors are the likely ΔNp63 effectors responsible for keratinocyte proliferation/stemness and suppression of differentiation, respectively, whereas IL-1a, IL-18, IL-24, and IL-36γ are the likely negative effectors responsible for suppression of inflammation. These data establish ΔNp63 as a critical node that coordinates epidermal homeostasis, stemness, and suppression of inflammation, upstream of known regulatory pathways.

Line-field confocal optical coherence tomography: New insights for psoriasis treatment monitoring.

BACKGROUND: Line-field confocal optical coherence tomography (LC-OCT) is a new, valid means for a rapid and non-invasive in vivo examination of the epidermis and upper dermis, allowing digital interpretation and measurement of high-resolution images on a cellular level. Given these properties, it may represent a valid tool for monitoring psoriasis during treatment, allowing a new method to set a precise objective severity of the disease. OBJECTIVES: We aimed to investigate the potentialities of LC-OCT in the non-invasive monitoring of microscopical changes associated with moderate-severe plaque psoriasis (PP) during the treatment with the most common biological drugs. MATERIALS AND METHODS: We performed LC-OCT imaging of PP lesions from 17 patients before and after 8 weeks of treatment. The clinical severity of the single lesions was evaluated using a lesion score (LS), designed considering three parameters: erythema, desquamation and infiltration. LC-OCT images were segmented by artificial intelligence and evaluated based on three microscopic criteria: the thickness of the stratum corneum, the thickness of the living epidermis and the undulation of the dermo-epidermal junction. RESULTS: Line-field confocal optical coherence tomography digital analysis allowed recognition and quantification of the three microscopic criteria, showing a reduction of all these during the follow-up. Furthermore, a high correlation between change in LS and the thickness of the stratum corneum and the thickness of the living epidermis was found. CONCLUSION: Line-field confocal optical coherence tomography can non-invasively monitor the response of PP to different treatments. Morphometric changes occurring in the psoriatic lesion during the 8-week treatment period were identified by in vivo LC-OCT and measured by using artificial intelligence. Although future studies are required, based on these preliminary results, LC-OCT may represent a valid potential tool for precise monitoring of therapeutic response.

From epidermal cells to functional pores: Understanding stomatal development.

Stomata, small hydromechanical valves in the leaf epidermis, are fundamental in regulating gas exchange and water loss between plants and the environment. Stomatal development involves a series of coordinated events ranging from the initial cell division that determines the meristemoid mother cells to forming specialized structures such as guard cells. These events are orchestrated by the transcription factors SPEECHLESS, FAMA, and MUTE through signaling networks. The role of plant hormones (e.g., abscisic acid, jasmonic acid, and brassinosteroids) in regulating stomatal development has been elucidated through these signaling cascades. In addition, environmental factors, such as light availability and CO2 concentration, also regulate the density and distribution of stomata in leaves, ultimately affecting overall water use efficiency. In this review, we highlight the mechanisms underlying stomatal development, connecting key signaling processes that activate or inhibit cell differentiation responsible for forming guard cells in the leaf epidermis. The factors responsible for integrating transcription factors, hormonal responses, and the influence of climatic factors on the signaling network that leads to stomatal development in plants are further discussed. Understanding the intricate connections between these factors, including the metabolic regulation of plant development, may enable us to maximize plant productivity under specific environmental conditions in changing climate scenarios.

Systemically administered wound-homing peptide accelerates wound healing by modulating syndecan-4 function.

CAR (CARSKNKDC) is a wound-homing peptide that recognises angiogenic neovessels. Here we discover that systemically administered CAR peptide has inherent ability to promote wound healing: wounds close and re-epithelialise faster in CAR-treated male mice. CAR promotes keratinocyte migration in vitro. The heparan sulfate proteoglycan syndecan-4 regulates cell migration and is crucial for wound healing. We report that syndecan-4 expression is restricted to epidermis and blood vessels in mice skin wounds. Syndecan-4 regulates binding and internalisation of CAR peptide and CAR-mediated cytoskeletal remodelling. CAR induces syndecan-4-dependent activation of the small GTPase ARF6, via the guanine nucleotide exchange factor cytohesin-2, and promotes syndecan-4-, ARF6- and Cytohesin-2-mediated keratinocyte migration. Finally, we show that genetic ablation of syndecan-4 in male mice eliminates CAR-induced wound re-epithelialisation following systemic administration. We propose that CAR peptide activates syndecan-4 functions to selectively promote re-epithelialisation. Thus, CAR peptide provides a therapeutic approach to enhance wound healing in mice; systemic, yet target organ- and cell-specific.

Linoleate-Containing Acylglucosylceramide, Acylceramide, and Events Associated with Formation of the Epidermal Permeability Barrier.

BACKGROUND: Linoleate-containing acylglucosylceramide (GLC-CER[EOx], where x = sphingosine [S], dihydrosphingosine [dS], phytosphingosine (P), or 6-hydroxysphingosine [H]) in the viable epidermis serve as the precursors to the linoleate-containing acylceramides (CER[EOx]) in the stratum corneum (SC) and the corneocyte lipid envelope (CLE), both of which are essential for the barrier function of the skin. SUMMARY: CLE formation and envelope maturation take place across the SC. Hypoxic conditions in the epidermis and anaerobic glycolysis with the production of lactic acid are important in proper SC barrier formation. KEY MESSAGE: CLE formation takes place across the SC. Its formation from linoleate-containing GLC-CER[EOx] requires lipoxygenase action, but anaerobic conditions leading to lactate production and hypoxia-inducible factors are essential for proper barrier formation. A number of unanswered questions are raised regarding formation of the CLE and the epidermal permeability barrier.