Role of vitamin D and calcium signaling in epidermal wound healing

PURPOSE

This review will discuss the role of vitamin D and calcium signaling in the epidermal wound response with particular focus on the stem cells of the epidermis and hair follicle that contribute to the wounding response.

METHODS

Selected publications relevant to the mechanisms of wound healing in general and the roles of calcium and vitamin D in wound healing in particular were reviewed.

RESULTS

Following wounding the stem cells of the hair follicle and interfollicular epidermis are activated to proliferate and migrate to the wound where they take on an epidermal fate to re-epithelialize the wound and regenerate the epidermis. The vitamin D and calcium sensing receptors (VDR and CaSR, respectively) are expressed in the stem cells of the hair follicle and epidermis where they play a critical role in enabling the stem cells to respond to wounding. Deletion of Vdr and/or Casr from these cells delays wound healing. The VDR is regulated by co-regulators such as the Med 1 complex and other transcription factors such as Ctnnb (beta-catenin) and p63. The formation of the Cdh1/Ctnn (E-cadherin/catenin) complex jointly stimulated by vitamin D and calcium plays a critical role in the activation, migration, and re-epithelialization processes.

CONCLUSION

Vitamin D and calcium signaling are critical for the ability of epidermal and hair follicle stem cells to respond to wounding. Vitamin D deficiency with the accompanying decrease in calcium signaling can result in delayed and/or chronic wounds, a major cause of morbidity, loss of productivity, and medical expense.

Stimulation with THBS4 activates pathways that regulate proliferation, migration and inflammation in primary human keratinocytes

As in other mammalian tissues, the extracellular matrix (ECM) of skin functions as mechanical support and regulative environment that guides the behavior of the cells. ECM is a gel-like structure that is primarily composed of structural and nonstructural proteins. While the content of structural proteins is stable, the level of nonstructural ECM proteins, such as thrombospondin-4 (THBS4), is dynamically regulated. In a previous work we demonstrated that THBS4 stimulated cutaneous wound healing. In this work we discovered that in addition to proliferation, THBS4 stimulated the migration of primary keratinocytes in 3D. By using a proteotransciptomic approach we found that stimulation of keratinocytes with THBS4 regulated the activity of signaling pathways linked to proliferation, migration, inflammation and differentiation. Interestingly, some of the regulated genes (eg IL37, TSLP) have been associated with the pathogenesis of atopic dermatitis (AD). We concluded that THBS4 is a promising candidate for novel wound healing therapies and suggest that there is a potential convergence of pathways that stimulate cutaneous wound healing with those active in the pathogenesis of inflammatory skin diseases.

Dasatinib causes keratinocyte apoptosis via inhibiting high mobility group Box 1-mediated mitophagy

Dasatinib, a second-generation BCR-ABL inhibitor, is currently used as first-line treatment for patients with chronic myeloid leukemia. However, dasatinib treatment increases the risk of severe cutaneous toxicity, which limits its long-term safe use in clinic. The underlying mechanism for dasatinib-induced cutaneous toxicity has not been clarified. In this study, we tested the toxicity of dasatinib on human immortal keratinocyte line (HaCaT) and normal human epidermal keratinocytes (NHEK). We found that dasatinib directly caused cytotoxicity on keratinocytes, which could be the explanation of the clinical characteristic of pathology. Mechanistically, dasatinib impaired mitophagy by downregulating HMGB1 protein level in keratinocytes, which led to the accumulation of dysfunctional mitochondria. Mitochondria-derived ROS caused DNA damage and cell apoptosis. More importantly, we confirmed that overexpression of HMGB1 could reverse dasatinib-induced keratinocyte apoptosis, and preliminarily explored the intervention effect of saikosaponin A, which could increase HMGB1 expression, on cutaneous toxicity caused by dasatinib. Collectively, our study revealed that dasatinib induced keratinocyte apoptosis via inhibiting HMGB1-mediated mitophagy and saikosaponin A could be a viable strategy for prevention of dasatinib-induced cutaneous toxicity.

Modelling of indirect cell-cell interaction networks mediated by IFNγ/IL-4 cytokine involved in atopic dermatitis

Atopic dermatitis (AD) is an immune-driven inflammatory skin disease that is known to have a significantly high life-time prevalence in the human population. T-helper (Th) immune cells play a key role in the pathogenesis of AD which is marked by defects in the skin barrier function along with a significant increase in the population of either Th1 or Th2 sub-types of Th cells. The progression of AD from the acute to chronic phase is still poorly understood, and here we explore the mechanism of this transition through the study of a mathematical model for indirect cell-cell interactions among Th and skin cells via the secreted cytokines IFNγ and IL-4, both known to have therapeutic potential. An increase in the level of cytokine IFN γ can catalyse the transition of AD from an acute to a chronic stage, while an increase in the level of cytokine IL-4 has the reverse effect. In our model, the transition of AD from the acute to chronic stage and vice versa can be abrupt (switch-like) with hysteresis: this bistable behaviour can potentially be used to keep AD in the acute phase since therapy based on suppression of IFNγ can retard the transition to the chronic phase.

Acute cytokine treatment stimulates glucose uptake and glycolysis in human keratinocytes

During inflammation, cellular glucose uptake and glycolysis are upregulated to meet an increased energy demand. For example, keratinocyte glycolysis is essential for progression of psoriasis. Therefore, understanding the regulation of glucose metabolism in keratinocytes is of importance. Here, we show that the pro-inflammatory cytokines IFNγ and TNF together rapidly induce glucose uptake, glycolysis, and glycolytic capacity in cultured keratinocytes. Furthermore, we found that acute IFNγ and TNF stimulation induces glucose transporter 4 (GLUT4) translocation to the plasma membrane and engages AMPK-dependent intracellular signaling. Together, these findings suggest acute cytokine-induced glucose metabolism in keratinocytes could contribute to inflammation in psoriatic disease, and that GLUT4 is involved in these processes.

First evidence of dermo-protective activity of marine sulfur-containing histidine compounds

Among natural products, ovothiol (ovo), produced by marine invertebrates, bacteria, and microalgae, is receiving increasing interest for its unique antioxidant properties. Recently, ovo has been shown to exhibit anti-inflammatory activity in an in vitro model of endothelial dysfunction and in an in vivo model of liver fibrosis. The aim of this study was to evaluate the effect of ovo and its precursor 5-thiohistidine (5-thio) in comparison with ergothioneine (erg), in human skin cells and tissues upon inflammation. We used both an in vitro and ex vivo model of human skin, represented by a keratinocytes cell line (HaCaT) and skin biopsies, respectively. We observed that ovo, 5-thio, and erg were not cytotoxic in HaCaT cells, but instead exerted a protective function against TNF-α -induced inflammation. In order to get insights on their mechanism of action, we performed western blot analysis of ERK and JNK, as well as sub-cellular localization of Nrf2, a key mediator of the anti-inflammatory response. The results indicated that the pre-treatment with ovo, 5-thio, and erg differently affected the phosphorylation of ERK and JNK. However, all the three molecules promoted the accumulation of Nrf2 in the nucleus of HaCaT cells. In addition, gene expression analysis by RTqPCR and ELISA assays performed in ex vivo human skin tissues pre-treated with thiohistidines and then inflamed with IL-1β revealed a significant downregulation of IL-8, TNF-α and COX-2 genes and a concomitant significant decrease in the cytokines IL-6, IL-8 and TNF-α production. Moreover, the protective action of ovo and 5-thio resulted to be stronger when compared with dexamethasone, a corticosteroid drug currently used to treat skin inflammatory conditions. Our findings suggest that ovo and 5-thio can ameliorate skin damage and may be used to develop natural skin care products to prevent the inflammatory status induced by environmental stressors and aging.

Screening of Plant-Derived Natural Extracts to Identify a Candidate Extract Capable of Enhancing Lipid Synthesis in Keratinocytes

BACKGROUND

Reduced lipid content in the stratum corneum is a major cause of skin-barrier dysfunction in various pathological conditions. Promoting lipid production is a potential strategy to improve skin-barrier function. Recent evidence supports the beneficial effects of adiponectin on lipid metabolism and senescence in keratinocytes.

OBJECTIVE

This study aimed to investigate whether plant extracts can enhance skin-barrier function.

METHODS

We screened fruit and herb extracts that enhance the lipid synthesis of keratinocytes via AMP-activated protein kinase (AMPK) activation and SIRT1 signaling in the adiponectin pathway. The levels of major lipid synthesis enzymes and transcription factors as well as epidermal barrier lipids involved in adiponectin-associated epidermal barrier formation were evaluated in the herbal extracts- or adiponectin-treated human epidermal keratinocyte and equivalent models. The mRNA expression of major lipid synthesis enzymes increased following treatment with Lycii Fructus , Prunus tomentosa , and Melia toosendan extracts.

RESULTS

The expression of transcription factors SIRT1, liver X receptor α, peroxisome proliferator-activated receptors (PPARs), and sterol regulatory element-binding proteins (SREBPs) were upregulated. Levels of free fatty acids, cholesterol, and ceramides were elevated. The expression of keratinocyte differentiation markers increased. In particular, among fruit extracts with a detectable effect, Melia toosendan induced the highest expression of lipid synthase.

CONCLUSION

These results indicate that Melia toosendan is a promising candidate for improving skin-barrier function.

The unfolded protein response gene Ire1α is required for tissue renewal and normal differentiation in the mouse tongue and esophagus

The IRE1α-XBP1s signaling branch of the unfolded protein response is a well-characterized survival pathway that allows cells to adapt to and resolve endoplasmic reticulum stress. Recent data has broadened our understanding of IRE1α-XBP1s signaling beyond a stress response and revealed a physiological mechanism required for the differentiation and maturation of a wide variety of cell types. Here we provide evidence that the IRE1α-XBP1s signaling pathway is required for the proliferation and maturation of basal keratinocytes in the mouse tongue and esophageal epithelium. Mice with conditional targeted deletion of either Ire1α or Xbp1 in keratin 14 expressing basal keratinocytes displayed severe thinning of the lingual and esophageal mucosa that rendered them unable to eat. In IRE1α null epithelium harvested at an earlier timepoint, genes regulating cell proliferation, cell-cell adhesion, and keratinization were significantly downregulated; indirect immunofluorescence revealed fewer proliferating basal keratinocytes, downregulation of E-cadherin, and thinning of the loricrin-positive granular and cornified layers. The number of Tp63-positive basal keratinocytes was reduced in the absence of IRE1α, and expression of the Wnt pathway transcription factor LEF1, which is required for the proliferation of lingual transit amplifying cells, was also significantly downregulated at the transcript and protein level. Together these results reveal an essential role for IRE1α-XBP1s in the maintenance of the stratified squamous epithelial tissue of the tongue and esophagus.

Transcriptomic analysis of mRNA expression in giant congenital melanocytic nevi

BACKGROUND AND OBJECTIVE

GCMN is a sporadic disease with an incidence ranging from 1/20,000 to 1/500000. So far, several studies have found that GCMN is related to somatic mutations, but most of them have focused on known pathogenic genes, and transcriptome sequencing based on large datasets is relatively uncommon. At present, the use of next-generation sequencing technologies and bioinformatics platforms makes genomic information study more comprehensive and efficient. In this study, the transcriptome differences between GCMN lesions and surrounding normal skin tissues were investigated using high-throughput transcriptome sequencing, and hub genes and pathways related to pathogenesis were identified, providing a theoretical foundation for further research into the pathogenesis of GCMN.

METHODS

Pathological skin tissue and surrounding normal skin tissue from GCMN patients, namely the pathological group (PG) and the control group (CG), were obtained. 1. All specimens were stained with HE to ensure that the samples met the experimental requirements. 2. Ten pairs of specimens were selected for high-throughput transcriptome sequencing, and the differentially expressed genes (DEGs) between the PG and the CG were obtained. The DEGs were analyzed by clusterProfiler R software for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The function of the subnetwork was analyzed and the hub genes were identified by the STRING database and Cytoscape software. 3. The expression differences of hub genes PTGS2, EGF, and SOX10 in pathological skin tissues and normal skin tissues were verified by qRT-PCR and immunofluorescence staining.

RESULTS

1. HE staining revealed a lot of melanocytes in the dermis and subcutaneous tissues. They were found around the hair follicles, sweat glands, sebaceous glands, and blood vessel walls, or in a specific pattern. 2. The screening threshold was set at p<0.01 and |log2fc|<1, and a total of 1163 DEGs were discovered between the PG and CG, with 519 genes up-regulated and 644 genes down-regulated in the pathological tissues. According to the GO functional analysis, 29 biological processes, 18 cell compositions, and 17 molecular functions were significantly enriched, with the majority of them being related to keratinocytes and the extracellular matrix. There were 779 nodes and 2359 interactions in the protein interaction network. Using the MCODE plug-in, the network was divided into 25 functional clusters. According to ClueGO results, Cluster5 was involved in melanin biosynthesis and melanocyte proliferation. Using 11 operation methods in the Cytohubba plug-in, PTGS2, EGF, and SOX10 in Cluster5 were chosen as hub genes. 3. qRT-PCR and immunofluorescent staining revealed that compared to normal skin tissue, the expression of SOX10 was significantly up-regulated, and the expression of PTGS2 and EGF was significantly down-regulated in pathological skin tissue(P<0.001).

CONCLUSIONS

In GCMN, keratinocytes and extracellular matrix may directly and indirectly affect melanocyte activity. PTGS2, EGF, and SOX10 are important genes and significantly differentially expressed in pathological and normal skin tissues. These findings may serve as a springboard for future research.

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.

Hormesis: wound healing and fibroblasts

Hormetic dose responses are reported here to occur commonly in the dermal wound healing process, with the particular focus on cell viability, proliferation, migration and collagen deposition of human and murine fibroblasts with in vitro studies. Hormetic responses were induced by a wide range of substances, including endogenous agents, pharmaceutical preparations, plant-derived extracts including many well-known dietary supplements, as well as physical stressor agents such as low-level laser treatments. Detailed mechanistic studies have identified common signaling pathways and their cross-pathway communications that mediate the hormetic dose responses. These findings complement and extend a similar comprehensive assessment concerning the occurrence of hormetic dose responses in keratinocytes. These findings demonstrate the generality of the hormetic dose response for key wound healing endpoints, suggesting that the hormesis concept has a fundamental role in wound healing, with respect to guiding strategies for experimental evaluation as well as therapeutic applications.

Cathepsin F is a potential marker for senescent human skin fibroblasts and keratinocytes associated with skin aging

Cellular senescence is characterized by cell cycle arrest and the senescence-associated secretory phenotype (SASP) and can be triggered by a variety of stimuli, including deoxyribonucleic acid (DNA) damage, oxidative stress, and telomere exhaustion. Cellular senescence is associated with skin aging, and identification of specific markers of senescent cells is essential for development of targeted therapies. Cathepsin F (CTSF) has been implicated in dermatitis and various cancers and participates in cell immortalization through its association with Bcl family proteins. It is a candidate therapeutic target to specifically label and eliminate human skin fibroblasts and keratinocytes immortalized by aging and achieve skin rejuvenation. In this study, we investigated whether CTSF is associated with senescence in human fibroblasts and keratinocytes. In senescence models, created using replicative aging, ionizing radiation exposure, and the anticancer drug doxorubicin, various senescence markers were observed, such as senescence-associated β-galactosidase (SA-β-gal) activity, increased SASP gene expression, and decreased uptake of the proliferation marker BrdU. Furthermore, CTSF expression was elevated at the gene and protein levels. In addition, CTSF-positive cells were abundant in aged human epidermis and in some parts of the dermis. In the population of senescent cells with arrested division, the number of CTSF-positive cells was significantly higher than that in the proliferating cell population. These results suggest that CTSF is a candidate for therapeutic modalities targeting aging fibroblasts and keratinocytes.

Pyrimethamine induces phototoxicity in human keratinocytes via lysosomal and mitochondrial dependent signaling pathways under environmental UVA and UVB exposure

Pyrimethamine (PYR) is used to treat parasitic infections including toxoplasmosis, pneumonia and cystoisosporiasis in HIV patients. Various oral medicines have shown phototoxicity therefore, we aimed to study the phototoxicity of PYR and its molecular mechanism involving stress responsive lysosomal protein Lamp2 and mitochondrial mediated signaling pathway under normal UVA/B exposure. We found that photodegradation and subsequent photoproduct formation was evident through LCMS/MS analysis. Photosensitized PYR produces ROS that cause damage to DNA, cell membrane and membrane bound organelles in human keratinocytes. PYR triggered cytotoxicity and phototoxicity that was evident through MTT and NRU assay respectively. Intracellular ROS generation caused phosphatidyl serine (PS) translocation in cell membrane, lysosome membrane permeabilization (LMP) and mitochondrial membrane potential (MMP) collapse that was further validated through caspase3 activation. DNA damage was measured as tail DNA formation and cell cycle arrest in G1 phase. Photosensitized PYR induces oxidative stress in the form of overexpression of Lamp2 that ultimately led to cellular apoptosis. Moreover, the effects of UVB were higher than UVA, probably due to its direct interaction with various macromolecules. We propose that photoexcited PYR may be harmful to human health even at normal sunlight exposure. Therefore, protective procedures should be practiced during PYR medication.

Sonodynamic therapy by phase-transition nanodroplets for reducing epidermal hyperplasia in psoriasis

The cross-talk between hyperproliferative keratinocytes and activated immune cells is responsible for the progression of psoriasis. The strategy to alleviate psoriasis through inhibiting the abnormal proliferation of keratinocytes remains challenging due to limited therapeutic effects and low skin penetration of drugs. Herein we designed an ultrasound-triggered phase-transition nanodroplet that could produce cavitation to enhance skin penetration and effectively generate reactive oxygen species (ROS) to induce keratinocyte apoptosis for psoriasis treatment. After ultrasound stimulation, the perfluoro-n-pentane (PFP) liquid core of the nanodroplets vaporized, and the Haematoporphyrin monomethyl ether (HMME) encapsulated in the nanodroplets generated plenty of intracellular ROS which caused the apoptosis of HaCat cells through inducing mitochondrial dysfunction. In addition, the blank nanodroplets successfully inhibited the secretion of IL-6 and TNF-α from macrophages and dendritic cells in vitro due to the anti-inflammatory effect of POPG. For the skin penetration test, the phase-transition nanodroplets could effectively accumulate in the epidermis of the skin and generate intracellular ROS. The in-vivo anti-psoriasis experiment demonstrated that the phase-transition nanodroplets relieved the symptoms of psoriasis lesion and inhibited epidermal hyperplasia through induction of cell apoptosis under ultrasound irritation. Meanwhile, the inflammatory cytokines in the skin lesion almost decreased to the normal baseline level after SDT. Collectively, this study demonstrated a new strategy to inhibit keratinocyte hyperproliferation for psoriasis management based on sonodynamic responded nanodroplets.

Astragaloside IV attenuates high glucose-induced human keratinocytes injury via TGF-β/Smad signaling pathway

OBJECTIVES

In this study, we have investigated the effect of Astragaloside IV on keratinocytes' proliferation, migration, oxidative stress, apoptosis, inflammation, and relevant signaling pathway, using human keratinocytes exposed to high glucose.

BACKGROUND

Astragaloside IV is one of the main active ingredients of Astragalus membranaceus (Fisch.) Bunge. Previous studies have found that Astragaloside IV exerts positive effects in various disease models and promotes wound healing.

METHODS

Cell proliferation and migration of keratinocytes, oxidative stress indicators, cell apoptosis rate, inflammatory factors, and key proteins in the TGF-β/Smad signaling pathway were evaluated by molecular biology/biochemical techniques, fluorescence microscope, and flow cytometry.

RESULTS

High glucose inhibited the cell proliferation and migration of keratinocytes, upregulated the levels of MDA, ROS, IL-6, IL-8, and Smad7, and decreased the levels of SOD, IL-10, TGF-β1, p-Smad2, and p-Smad3. Astragaloside IV attenuated the dysfunction of keratinocytes, oxidative stress, cell apoptosis, and inflammation, but activated TGF-β/Smad signaling pathway. Meanwhile, the addition of SB431542 (the inhibitor of TGF-β/Smad signaling pathway) eliminated the impact of Astragaloside IV on high glucose-induced keratinocytes.

CONCLUSIONS

These results strongly suggest that Astragaloside IV may be a potential drug candidate for accelerating diabetic wound healing, by protecting keratinocytes against damages induced by high glucose and TGF-β/Smad pathway is involved in this process at the cellular level.

Hormesis: Wound healing and keratinocytes

Hormetic dose responses (i.e., a biphasic dose/concentration response characterized by a low dose stimulation and a high dose inhibition) are shown herein to be commonly reported in the dermal wound healing process, with the particular focus on cell viability, proliferation, and migration of human keratinocytes in in vitro studies. Hormetic responses are induced by a wide range of substances, including endogenous agents, numerous drug and nanoparticle preparations and especially plant derived extracts, including many well-known dietary supplements as well as physical stressor agents, such as low-level laser treatments. Detailed mechanistic studies have identified common signaling pathways and their cross-pathway communications that mediate the hormetic dose responses. These findings suggest that the concept of hormesis plays a fundamental role in wound healing, with important potential implications for agent screening and evaluation, as well as clinical strategies.

Intraoperative assessment of surgical margins using "en face" frozen sections in the management of cutaneous carcinomas

Background

Basal cell and squamous cell carcinomas (BCC and SCC) are the most common types of cancer worldwide. Intraoperative assessment of surgical margins by frozen section has been widely used to ensure disease-free margins. The intraoperative “en face” freezing technique evaluates all peripheral and deep margins.

Objective

To report the results of the “en face” freezing technique in relation to tumor recurrence and agreement with paraffin-embedded tissue examination.

Methods

Retrospective analysis of patients undergoing surgical excision of BCC and SCC at the A. C. Camargo Cancer Center, Brazil.

Results

This study included 542 skin carcinomas, which were excised from 397 patients. A total of 201 male patients (50.6%), and 196 female patients (49.4%) were assessed, whose mean age was 64 years. The tumors were mostly located on the head and neck region (87.8%). BCC corresponded to 79.7% of the cases. The mean follow-up was 38 months. Tumor relapse occurred in 0.86% of the primary tumors and 3.7% of recurrent tumors. The result of the intraoperative “en face” frozen section evaluation was in agreement with the final result of the anatomopathological examination (paraffin test) in 98% of the lesions.

Study limitations

Not having a minimum follow-up time of 5 years for all patients.

Conclusion

The “en face” freezing technique shows low tumor relapse, being reliable and safe to guarantee negative surgical margins of the tumor.

Scutellarein Attenuates Atopic Dermatitis by Selectively Inhibiting Transient Receptor Potential Vanilloid 3

BACKGROUND AND PURPOSE

Atopic dermatitis (AD) is one of the most common chronic inflammatory cutaneous diseases with unmet clinical needs. As a common ingredient found in several medicinal herbs with efficacy on cutaneous inflammatory diseases, Scutellarein (Scu) has been shown to possess anti-inflammatory and anti-proliferative activities. We aimed to evaluate the therapeutic efficacy of Scu against AD and its underlying molecular mechanism.

EXPERIMENTAL APPROACH

Efficacy of Scu on AD was evaluated in 2,4-dinitrofluorobenzene (DNFB) and carvacrol-induced dermatitis mouse models. Cytokine mRNA and serum IgE levels were examined using qPCR and ELISA, respectively. Voltage clamp recordings were used to measure currents mediated by transient receptor potential (TRP) channels. In silico docking, site-direct mutagenesis, and covalent modification were used to explore the binding pocket of Scu on TRPV3.

KEY RESULTS

Subcutaneous administration of Scu efficaciously suppresses DNFB and carvacrol-induced pruritus, epidermal hyperplasia and skin inflammation in wild type mice but has no additional benefit in Trpv3 knockout mice in the carvacrol model. Scu is a potent and selective TRPV3 channel allosteric negative modulator with an apparent affinity of 1.18 μM. Molecular docking coupled with site-direct mutagenesis and covalent modification of incorporated cysteine residues demonstrate that Scu targets the cavity formed between the pore helix and transmembrane helix S6. Moreover, Scu attenuates endogenous TRPV3 activity in human keratinocytes and inhibits carvacrol-induced proliferative and proinflammatory responses.

CONCLUSIONS AND IMPLICATIONS

Collectively, these data demonstrate that Scu ameliorates carvacrol-induced skin inflammation by directly inhibiting TRPV3, and TRPV3 represents a viable therapeutic target for AD treatment.

Cobalt protoporphyrin promotes human keratinocyte migration under hyperglycemic conditions

Background

Complete healing of diabetic wounds continues to be a clinically unmet need. Although robust therapies such as stem cell therapy and growth factor treatment are clinically applied, these treatments are costly for most diabetic wound patients. Therefore, a cheaper alternative is needed. Cobalt protoporphyrin (CoPP) has recently been demonstrated to promote tissue regeneration. In this study, the therapeutic benefits of CoPP in diabetic wound healing were examined.

Methods

An in vitro wound healing model that mimics re-epithelialization was established to examine the effect of CoPP on the migratory capability of human keratinocytes (HaCaT) in either normal glucose (NG) or high glucose (HG) media, as well as in the presence of either H₂O₂ or lipopolysaccharide (LPS). At the end of the migration assays, cells were collected and subjected to Western blotting analysis and immunostaining.

Results

HaCaT were found to migrate significantly more slowly in the HG media compared to the NG media. CoPP treatment was found to enhance cell migration in HG media, but was found to decrease cell migration and proliferation when HaCaT were cultured in NG media. CoPP treatment induced high levels of expression of Nrf-2/HO-1 and FoxO1 in HaCaT cultured in either glucose concentration, although the FoxO1 expression was found to be significantly higher in HaCaT that underwent the migration assay in NG media compared to those in HG media. The higher level of FoxO1 expression seen in CoPP-treated HaCaT cultured in NG media resulted in upregulation of CCL20 and downregulation of TGFβ1. In contrast, HaCaT migrated in HG media were found to have high levels of expression of TGFβ1, and low levels of expression of CCL20. Interestingly, in the presence of H₂O₂, CoPP-pretreated HaCaT cultured in either NG or HG media had similar expression level of Nrf-2/HO-1 and FoxO1 to each other. Moreover, the anti-apoptotic effect of CoPP pretreatment was noticed in HaCaT cultured in either glucose concentration. Additionally, CoPP pretreatment was shown to promote tight junction formation in HaCaT suffering from LPS-induced damage.

Conclusions

CoPP enhances cell migratory capacity under hyperglycemic conditions, and protects cells from oxidative and LPS-induced cellular damage in HG media containing either H₂O₂ or LPS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00499-0.

Exosomes from human induced pluripotent stem cells-derived keratinocytes accelerate burn wound healing through miR-762 mediated promotion of keratinocytes and endothelial cells migration

Background

The use of keratinocytes derived from induced pluripotent stem cells (iPSCs-KCs) may represent a novel cell therapy strategy for burn treatment. There is growing evidence that extracellular vesicles, including exosomes, are primary mediators of the benefits of stem cell therapy. Herein, we thus explored the effects of exosomes produced by iPSCs-derived keratinocytes (iPSCs-KCs-Exos) in a model of deep second-degree burn wound healing and evaluated the mechanistic basis for the observed activity.

Methods

iPSCs-KCs-Exos were isolated from conditioned medium of iPSCs-KCs and verified by electron micrograph and size distribution. Next, iPSCs-KCs-Exos were injected subcutaneously around wound sites, and its efficacy was evaluated by measuring wound closure areas, histological examination, and immunohistochemistry staining. The effects of iPSCs-KCs-Exos on proliferation and migration of keratinocytes and endothelial cells in vitro were assessed by EdU staining, wound healing assays, and transwell assay. Then, high-throughput microRNA sequencing was used to explore the underlying mechanisms. We assessed the roles of miR-762 in iPSCs-KCs-Exos-induced regulation of keratinocytes and endothelial cells migration. Furthermore, the target gene which mediated the biological effects of miR-762 in keratinocytes and endothelial cells was also been detected.

Results

The analysis revealed that iPSCs-KCs-Exos application to the burn wound drove the acceleration of wound closure, with more robust angiogenesis and re-epithelialization being evident. Such iPSCs-KCs-Exos treatment effectively enhanced endothelial cell and keratinocyte migration in vitro. Moreover, the enrichment of miR-762 was detected in iPSCs-KCs-Exos and was found to target promyelocytic leukemia (PML) as a means of regulating cell migration through a mechanism tie to integrin beta1 (ITGB1).

Conclusion

These results thus provide a foundation for the further study of iPSCs-KCs-Exos as novel cell-free treatments for deep second-degree burns.

Graphical Abstract

Transforming growth factor-β1 negatively regulates SOCS7 via EGR1 during wound healing

Background

TGF-β1 promotes keratinocyte migration and re-epithelialization of cutaneous wounds during the wound healing process. Decreased SOCS7 expression has been associated with increased healing potential. However, the relationship between TGF-β1 and SOCS7 in wound re-epithelialization remains unclear.

Objectives

To investigate the relationship between TGF-β1 and SOCS7 in the re-epithelialization of keratinocytes during skin wound healing.

Methods

The expression of SOCS7 under different concentrations of TGF-β1 was detected by WB and qPCR. The migration ability of keratinocytes was detected by scratch and Transwell assay. Protein interactions were detected by ChIP and luciferase assay. The effect of SOCS7 on skin healing in mice was detected in animal model.

Results

In this study, we found that SOCS7 was downregulated by TGF-β1 and that overexpression of SOCS7 led to suppression of TGF-β1-induced keratinocyte migration through inhibition of the PI3K/AKT and MEK/ERK pathways. Also, TGF-β1 negatively regulated SOCS7 expression at the transcriptional level through the binding of EGR1 to the EGR1/SP1 overlapping binding sites in the SOCS7 promoter.

Conclusion

Taken together, our findings show that TGF-β1-induced EGR1 expression is required for repression of SOCS7, which promotes keratinocyte migration and re-epithelialization during wound healing. Finally, our study identifies the TGF-β1/EGR1/SOCS7 pathway as a potential therapeutic target to promote wound healing.

In vitro and in vivo correlation of skin and cellular responses to nucleic acid delivery

Skin, the largest organ in the body, provides a passive physical barrier against infection and contains elements of the innate and adaptive immune systems. Skin consists of various cells, including keratinocytes, fibroblasts, endothelial cells and immune cells. This diversity of cell types could be important to gene therapies because DNA transfection could elicit different responses in different cell types. Previously, we observed the upregulation and activation of cytosolic DNA sensing pathways in several non-tumor and tumor cell types as well in tumors after the electroporation (electrotransfer) of plasmid DNA (pDNA). Based on this research and the innate immunogenicity of skin, we correlated the effects of pDNA electrotransfer to fibroblasts and keratinocytes to mouse skin using reverse transcription real-time PCR (RT-qPCR) and several types of protein quantification. After pDNA electrotransfer, the mRNAs of the putative DNA sensors DEAD (AspGlu-Ala-Asp) box polypeptide 60 (Ddx60), absent in melanoma 2 (Aim2), Z-DNA binding protein 1 (Zbp1), interferon activated gene 202 (Ifi202), and interferon-inducible protein 204 (Ifi204) were upregulated in keratinocytes, while Ddx60, Zbp1 and Ifi204 were upregulated in fibroblasts. Increased levels of the mRNAs and proteins of several cytokines and chemokines were detected and varied based on cell type. Mouse skin experiments in vivo confirmed our in vitro results with increased expression of putative DNA sensor mRNAs and of the mRNAs and proteins of several cytokines and chemokines. Finally, with immunofluorescent staining, we demonstrated that skin keratinocytes, fibroblasts and macrophages contribute to the immune response observed after pDNA electrotransfer.

Therapeutic Potential of Skin Stem Cells and Cells of Skin Origin: Effects of Botanical Drugs Derived from Traditional Medicine

Skin, the largest organ of the body, plays a vital role in protecting inner organs. Skin stem cells (SSCs) comprise a group of cells responsible for multiplication and replacement of damaged and non-functional skin cells; thereby help maintain homeostasis of skin functions. SSCs and differentiated cells of the skin such as melanocytes and keratinocytes, have a plethora of applications in regenerative medicine. However, as SSCs reside in small populations in specific niches in the skin, use of external stimulants for cell proliferation in vitro and in vivo is vital. Synthetic and recombinant stimulants though available, pose many challenges due to their exorbitant prices, toxicity issues and side effects. Alternatively, time tested traditional medicine preparations such as polyherbal formulations are widely tested as effective natural stimulants, to mainly stimulate proliferation, and melanogenesis/prevention of melanogenesis of both SSCs and cells of skin origin. Complex, multiple targets, synergistic bioactivities of the phytochemical constituents of herbal preparations amply justify these as natural stimulants. The use of these formulations in clinical applications such as in skin regeneration for burn wounds, wound healing acceleration, enhancement or decrease of melanin pigmentations will be in great demand. Although much multidisciplinary research is being conducted on the use of herbal formulas as stem cell stimulants, very few related clinical trials are yet registered with the NIH clinical trial registry. Therefore, identification/ discovery, in depth investigations culminating in clinical trials, as well as standardization and commercialization of such natural stimulants must be promoted, ensuring the sustainable use of medicinal plants.

Dietary olive oil intake aggravates psoriatic skin inflammation in mice via Nrf2 activation and polyunsaturated fatty acid imbalance

Psoriasis is a chronic inflammatory skin disease, which does not have effective treatment options. However, olive oil has been suggested as an alternative to treat psoriasis, but no study has evaluated the mechanisms involved in the effects of olive oil on psoriasis. Thus, the current study investigated whether olive oil could ameliorate psoriasiform skin inflammation. To test this, mice received topical application of imiquimod to induce inflammation and were treated orally with olive oil. Human immortalized keratinocytes were also treated with imiquimod and olive oil. Epidermal thickness and keratinocyte proliferation were increased in imiquimod-induced lesions of olive-oil-treated animals. In both in vitro and in vivo studies, protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2) were elevated following imiquimod and olive oil administration. Inhibition of Nrf2 abolished the increased proliferation of keratinocytes treated with imiquimod and olive oil, demonstrating the role of Nrf2 in olive oil-mediated exacerbation of psoriasiform skin inflammation. In addition, lower levels of linoleic acid and higher levels of oleic acid were observed in imiquimod- and olive-oil-treated animals, which may also contribute to the adverse effects of olive oil on psoriasis. In conclusion, dietary intake of olive oil aggravates the symptoms of psoriatic skin lesions through the overexpression of Nrf2 and an imbalance in oleic and linoleic acids levels, suggesting that a diet rich in olive oil may have significant negative effects on psoriasis.

Staphylococcus aureus Activates the Aryl Hydrocarbon Receptor in Human Keratinocytes

Staphylococcus aureus is an important pathogen causing various infections, including - as most frequently isolated bacterium - cutaneous infections. Keratinocytes as the first barrier cells of the skin respond to S. aureus by the release of defense molecules such as cytokines and antimicrobial peptides. Although several pattern recognition receptors expressed in keratinocytes such as Toll-like and NOD-like receptors have been reported to detect the presence of S. aureus, the mechanisms underlying the interplay between S. aureus and keratinocytes are still emerging. Here, we report that S. aureus induced gene expression of CYP1A1 and CYP1B1, responsive genes of the aryl hydrocarbon receptor (AhR). AhR activation by S. aureus was further confirmed by AhR gene reporter assays. AhR activation was mediated by factor(s) <2 kDa secreted by S. aureus. Whole transcriptome analyses and real-time PCR analyses identified IL-24, IL-6, and IL-1beta as cytokines induced in an AhR-dependent manner in S. aureus-treated keratinocytes. AhR inhibition in a 3D organotypic skin equivalent confirmed the crucial role of the AhR in mediating the induction of IL-24, IL-6, and IL-1beta upon stimulation with living S. aureus. Taken together, we further highlight the important role of the AhR in cutaneous innate defense and identified the AhR as a novel receptor mediating the sensing of the important skin pathogen S. aureus in keratinocytes.