Regulation Of Keratinocyte Differentiation Research Articles

A feedback loop between plakophilin 4 and YAP signaling regulates keratinocyte differentiation

The Hippo signaling pathway is an important regulator of organ growth and differentiation, and its deregulation contributes to the development of cancer. The activity of its downstream targets YAP/TAZ depends on adherens junctions. Plakophilin 4 (PKP4) is a cell-type specific adherens junction protein expressed in the proliferating cells of the epidermis. Here, we show that PKP4 diminishes proliferation as well as differentiation. Depletion of PKP4 increased proliferation but at the same time induced premature epidermal differentiation. PKP4 interacted with several Hippo pathway components, including the transcriptional co-activators YAP/TAZ, and promoted nuclear YAP localization and target gene expression. In differentiated keratinocytes, PKP4 recruited LATS and YAP to cell junctions where YAP is transcriptionally inactive. YAP depletion, on the other hand, reduced PKP4 levels and keratinocyte adhesion indicative of a feedback mechanism controlling adhesion, proliferation, and differentiation by balancing YAP functions.

LncRNA LINC00941 modulates MTA2/NuRD occupancy to suppress premature human epidermal differentiation.

Numerous long non-coding RNAs (lncRNAs) were shown to have a functional impact on cellular processes such as human epidermal homeostasis. However, the mechanism of action for many lncRNAs remains unclear to date. Here, we report that lncRNA LINC00941 regulates keratinocyte differentiation on an epigenetic level through association with the NuRD complex, one of the major chromatin remodelers in cells. We find that LINC00941 interacts with NuRD-associated MTA2 and CHD4 in human primary keratinocytes. LINC00941 perturbation changes MTA2/NuRD occupancy at bivalent chromatin domains in close proximity to transcriptional regulator genes, including the EGR3 gene coding for a transcription factor regulating epidermal differentiation. Notably, LINC00941 depletion resulted in reduced NuRD occupancy at the EGR3 gene locus, increased EGR3 expression in human primary keratinocytes, and increased abundance of EGR3-regulated epidermal differentiation genes in cells and human organotypic epidermal tissues. Our results therefore indicate a role of LINC00941/NuRD in repressing EGR3 expression in non-differentiated keratinocytes, consequentially preventing premature differentiation of human epidermal tissues.

The human testis-enriched HSPA2 interacts with HIF-1α in epidermal keratinocytes, yet HIF-1α stability and HIF-1-dependent gene expression rely on the HSPA (HSP70) activity

The Hypoxia-Inducible Factor 1 (HIF-1) is essential for cellular adaptation to reduced oxygen levels. It also facilitates the maintenance and re-establishment of skin homeostasis. Among others, it is involved in regulating keratinocyte differentiation. The stability of the oxygen-liable HIF-1α subunit is regulated by various non-canonical oxygen-independent mechanisms, which among others involve Heat Shock Proteins of the A family (HSPA/HSP70). This group of highly homologous chaperones and proteostasis-controlling factors includes HSPA2, a unique member crucial for spermatogenesis and implicated in the regulation of keratinocyte differentiation. HIF-1 can control the HSPA2 gene expression.In this study, we revealed that HIF-1α is the first confirmed client of HSPA2 in human somatic cells. It colocalises and interacts directly with HSPA2 in the epidermis in situ and immortalised keratinocytes in vitro. Using an in vitro model based on HSPA2-overexpressing and HSPA2-deficient variants of immortalised keratinocytes we showed that changes in HSPA2 levels do not affect the levels and intracellular localisation of HIF-1α or influence the ability of HIF-1 to modulate target gene expression. However, HIF-1α stability in keratinocytes appears critically reliant on HSPAs as a group of functionally overlapping chaperones. In addition to HSPA2, HIF-1α colocalises and forms complexes with HSPA8 and HSPA1, representing housekeeping and stress-inducible HSPA family paralogs, respectively. Chemical inhibition of HSPA activity, but not paralog-specific knockdown of HSPA8 or HSPA1 expression reduced HIF-1α levels and HIF-1-dependent gene expression. These observations suggest that pharmacological targeting of HSPAs could prevent excessive HIF-1 signalling in pathological skin conditions.

Research advancements in the immunomodulating effect of sphingosine-1-phosphate in skin diseases

Sphingosine-1-phosphate (S1P) is a bioactive lipid metabolite that acts as an extracellular and intracellular messenger in a variety of biological activities, many of which are mediated by binding to S1P-specific G protein-coupled receptors. S1P receptors can affect cell fate by mediating cell differentiation, proliferation, and apoptosis. S1P mainly plays an immunomodulatory role in vivo. In recent years, increasing numbers of studies have shown that S1P is involved in the occurrence and development of immune-related skin diseases by regulating keratinocyte differentiation, proliferation, and apoptosis; lymphocyte migration; and angiogenesis. This review explores the metabolism and signal transduction mechanism of S1P, focusing on research advancements in the immune regulation function of S1P and its impact on immune-related skin diseases. The aim is to provide insights that can contribute to the research and application of S1P in immune-related skin diseases.

Exploring the Effect of Xiao-Chai-Hu Decoction on Treating Psoriasis Based on Network Pharmacology and Experiment Validation.

Psoriasis is a chronic, inflammatory and recurrent skin disease. Xiao-Chai-Hu Decoction (XCHD) has shown good effects against some inflammatory diseases and cancers. However, the pharmacological effect and mechanisms of XCHD on psoriasis are not yet clear. To uncover the effect and mechanisms of XCHD on psoriasis by integrating network pharmacology, molecular docking, and in vivo experiments. The active ingredients and corresponding targets of XCHD were screened through Traditional Chinese Medicine Systems Pharmacology Database and Analysis (TCMSP) and Traditional Chinese Medicine Integrated Database (TCMID). Differentially expressed genes (DEGs) of psoriasis were obtained from the gene expression omnibus (GEO) database. The XCHD-psoriasis intersection targets were obtained by intersecting XCHD targets, and DEGs were used to establish the "herb-active ingredient-target" network and Protein-Protein Interaction (PPI) Network. The hub targets were identified based on the PPI network by Cytoscape software. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were performed next. Molecular docking was executed via AutoDockTools-1.5.6. Finally, in vivo experiments were carried out further to validate the therapeutic effects of XCHD on psoriasis. 58 active components and 219 targets of XCHD were screened. 4 top-active components (quercetin, baicalein, wogonin and kaempferol) and 7 hub targets (IL1B, CXCL8, CCND1, FOS, MMP9, STAT1 and CCL2) were identified. GO and KEGG pathway enrichment analyses indicated that the TNF signaling pathway, IL-17 signaling pathway and several pathways were involved. Molecular docking results indicated that hub genes had a good affinity to the corresponding key compounds. In imiquimod (IMQ)-induced psoriasis mouse models, XCHD could significantly improve psoriasis-like skin lesions, downregulate KRT17 and Ki67, and inhibit inflammation cytokines and VEGF. XCHD showed the therapeutic effect on psoriasis by regulating keratinocyte differentiation, and suppressing inflammation and angiogenesis, which provided a theoretical basis for further experiments and clinical research.

P39 Methotrexate induces epidermal DNA damage response and filaggrin in atopic eczema

Abstract Methotrexate (MTX) is an effective treatment for atopic eczema (AE), but its mechanism of action remains undefined. Our previous work identified keratinocytes as a direct target of MTX by increasing epidermal differentiation. Evidence supports the concept of DNA damage-induced keratinocyte differentiation; however, this has not been characterized in the context of MTX. We tested the hypothesis that MTX may act therapeutically in AE by inducing DNA damage and activating downstream DNA damage response signalling pathways. Patients with AE starting MTX (initial dose 10 mg weekly) were recruited (n = 12). The FLG status was determined by DNA genotyping. Clinical data and skin biopsies from lesional and nonlesional skin were collected at week 0 (baseline), week 2 [visit 1 (V1)] and week 12 [visit 2 (V2)] following MTX initiation. γH2A.X, a marker of DNA damage, was quantified to explore the relationship between DNA damage secondary to MTX treatment and FLG status. γH2A.X and filaggrin protein epidermal immunostaining were quantified. The male-to-female ratio was 8 : 4 and median participant age was 45 years. Median Eczema Area and Severity Index (EASI) score improved from 23.5 (baseline, n = 12) to 14.6 at V1 (n = 12) and 9.0 at V2 (n = 8). Median Dermatology Life Quality Index reduced from 15 (baseline, n = 12) to 10.5 (V2, n = 8). Four patients were FLG heterozygotes and eight were FLG wild type. In combined analysis of all patients, epidermal γH2A.X increased in lesional skin at both time points [n = 6 (V1: P = 0.022; V2: P = 0.009)] and in nonlesional skin by V2 (n = 6; P = 0.021). γH2A.X increased in lesional skin at V2 in both FLG heterozygotes (P = 0.044) and wild types (P = 0.038). Epidermal filaggrin in lesional and nonlesional skin increased at V1 and V2 in all patients combined (n = 5; P = 0.029). Filaggrin increased in the nonlesional skin of FLG heterozygotes (P = 0.044) and in the lesional skin of FLG wild-type patients (P = 0.009) by V2. Transcriptomic (RNAseq) analysis was performed on skin biopsies (n = 11 patients; n = 42 samples). We explored the relationship of gene expression with severity (EASI) and FLG status. AKR1B10, IL22 and LGALS7 expression increased with disease severity. The AKR1B10 (regulates keratinocyte differentiation) and LGALS7 expression (expressed during barrier dysfunction) response with EASI was enhanced in FLG heterozygotes vs. wild-type patients. Canonical pathways were upregulated in lesional skin at V2 vs. baseline. Through epidermal immunostaining and transcriptomic gene analysis, we demonstrated evidence of DNA damage and filaggrin induction in patients with AE following MTX therapy, with associated improved disease outcomes.

AHNAK, regulated by the OSM/OSMR signaling, involved in the development of primary localized cutaneous amyloidosis

BackgroundPrimary localized cutaneous amyloidosis (PLCA) is a chronic skin disease characterized by aberrant keratinocyte differentiation, epidermal hyperproliferation, and amyloid deposits. Previously, we demonstrated OSMR loss-function mutants enhanced basal keratinocyte differentiation through the OSMR/STAT5/KLF7 signaling in PLCA patients. ObjectiveTo investigate the underlying mechanisms involved in basal keratinocyte proliferation in PLCA patients that remain unclear. MethodsPatients with pathologically confirmed PLCA visiting the dermatologic outpatient clinic were involved in the study. Laser capture microdissection and mass spectrometry analysis, gene-edited mice, 3D human epidermis culture, flow cytometry, western blot, qRT-PCR and RNA sequencing were used to explore the underlying molecular mechanisms. ResultsIn this study, we found that AHNAK peptide fragments were enriched in the lesions of PLCA patients, as detected by laser capture microdissection and mass spectrometry analysis. The upregulated expression of AHNAK was further confirmed using immunohistochemical staining. qRT-PCR and flow cytometry revealed that pre-treatment with OSM can inhibit AHNAK expression in HaCaT cells, NHEKs, and 3D human skin models, but OSMR knockout or OSMR mutations abolished this down-regulation trend. Similar results were obtained in wild-type and OSMR knockout mice. More importantly, EdU incorporation and FACS assays demonstrated the knockdown of AHNAK could induce G1 phase cell cycle arrest and inhibit keratinocyte proliferation. Furthermore, RNA sequencing revealed that AHNAK knockdown regulated keratinocyte differentiation. ConclusionTaken together, these data indicated that the elevated expression of AHNAK by OSMR mutations led to hyperproliferation and overdifferentiation of keratinocytes, and the discovered mechanism might provide insights into potential therapeutic targets for PLCA.

Weighted Gene Co-Expression Network Analysis of Oxymatrine in Psoriasis Treatment.

Psoriasis is a common, chronic, inflammatory, recurrent, immune-mediated skin disease. Oxymatrine is effective for treating moderate and severe psoriasis. Here, transcriptional changes in skin lesions before and after oxymatrine treatment of patients with psoriasis were identified using full-length transcriptome analysis and then compared with those of normal skin tissues. Co-expression modules were constructed by combining the psoriasis area and severity index (PASI) score with weighted gene co-expression network analysis to explore the action mechanism of oxymatrine in improving clinical PASI. The expression of selected genes was verified using immunohistochemistry, quantitative real-time PCR, and Western blotting. Kyoto Encyclopedia of Gene and Genome pathway analysis revealed that oxymatrine treatment reversed the abnormal pathways, with an improvement in lesions and a reduction in PASI scores. Gene Ontology (GO) analysis revealed that oxymatrine treatment led to altered GO terms being regulated with a decrease in the PASI score in patients. Therefore, oxymatrine treatment may improve the skin barrier, differentiation of keratinocytes, and alleviate abnormality of organelles such as desmosomes. Protein-protein interaction network interaction analysis revealed that the top five hub genes among many interrelated genes were CNFN, S100A8, SPRR2A, SPRR2D, and SPRR2E, associated with the epidermal differentiation complex (EDC). EDC regulates keratinocyte differentiation. This result indicates that oxymatrine treatment can restore keratinocyte differentiation by regulating the expression of EDC-related genes. Oxymatrine can improve erythema, scales, and other clinical symptoms of patients with psoriasis by regulating EDC-related genes and multiple pathways, thereby promoting the repair of epithelial tissue and maintaining the dynamic balance of skin keratosis.

Skin programming of inflammatory responses to Staphylococcus aureus is compartmentalized according to epidermal keratinocyte differentiation status.

Acute cutaneous inflammation causes microbiome alterations as well as ultrastructural changes in epidermis stratification. However, the interactions between keratinocyte proliferation and differentiation status and the skin microbiome have not been fully explored. Hypothesizing that the skin microbiome contributes to regulation of keratinocyte differentiation and can modify antimicrobial responses, we examined the effect of exposure to commensal (Staphylococcus epidermidis, SE) or pathogenic (Staphylococcus aureus, SA) challenge on epidermal models. Explant biopsies were taken to investigate species-specific antimicrobial effects of host factors. Further investigations were performed in reconstituted epidermal models by bulk transcriptomic analysis alongside secreted protein profiling. Single-cell RNA sequencing analysis was performed to explore the keratinocyte populations responsible for SA inflammation. A dataset of 6391 keratinocytes from control (2044 cells), SE challenge (2028 cells) and SA challenge (2319 cells) was generated from reconstituted epidermal models. Bacterial lawns of SA, not SE, were inhibited by human skin explant samples, and microarray analysis of three-dimensional epidermis models showed that host antimicrobial peptide expression was induced by SE but not SA. Protein analysis of bacterial cocultured models showed that SA exposure induced inflammatory mediator expression, indicating keratinocyte activation of other epidermal immune populations. Single-cell DropSeq analysis of unchallenged naive, SE-challenged and SA-challenged epidermis models was undertaken to distinguish cells from basal, spinous and granular layers, and to interrogate them in relation to model exposure. In contrast to SE, SA specifically induced a subpopulation of spinous cells that highly expressed transcripts related to epidermal inflammation and antimicrobial response. Furthermore, SA, but not SE, specifically induced a basal population that highly expressed interleukin-1 alarmins. These findings suggest that SA-associated remodelling of the epidermis is compartmentalized to different keratinocyte populations. Elucidating the mechanisms regulating bacterial sensing-triggered inflammatory responses within tissues will enable further understanding of microbiome dysbiosis and inflammatory skin diseases, such as atopic eczema.

Enhanced BMP signaling through ALK2 attenuates keratinocyte differentiation

Accumulated studies have suggested that bone morphogenetic proteins (BMPs) are critical for skin development. However, it remains elusive how BMP signaling via ALK2 (aka ACVR1), one of the important BMP type I receptors, regulates keratinocyte differentiation. To address this question, we utilized a genetic system that enhances BMP signaling via ALK2 in an epidermis-specific manner in mice (hereafter ca-Alk2:K14-Cre). Ca-Alk2:K14-Cre mice displayed a sticky and hairless skin phenotype with a thinner epidermis incapable of differentiating. Although cellular proliferation and survival were comparable between wild-type and ca-Alk2:K14-Cre mice, skin differentiation was severely hampered in ca-Alk2:K14-Cre mice. To uncover the mechanism of altered keratinocyte differentiation, we performed a transcriptome analysis. As a result, we found that the expression levels of cell cycle inhibitor p21 were increased in ca-Alk2:K14-Cre mice. Our findings suggest that aberrant BMP signaling via ALK2 positively regulates p21 expression that attenuates keratinocyte differentiation, and further highlights the critical role of BMP signaling in skin development.

775 Structural and molecular similarities between plantar and wound keratinocytes - is the foot a chronic wound?

Plantar skin is known for specializations such as lack of hair, accelerated epidermal turnover, poor barrier function, and expression of cytokeratin 9, but both clinically and scientifically it is often regarded as just thicker versions of “normal” skin. Using the porcine model (which we have found shares many structural and molecular similarities with human plantar skin, more so than rodent models), we recently found that plantar skin is more distinctive than previously recognized, including a unique gene expression profile, and substantial alterations in both tissue calcium distribution and store-operated calcium entry response, with broad implications as calcium is both a key regulator of keratinocyte differentiation and a critical component in second messenger signaling.

SerpinB7 deficiency contributes to development of psoriasis via calcium-mediated keratinocyte differentiation dysfunction

Defective execution of proteases and protease inhibitors that mediate abnormal signaling cascades is emerging as a key contributor to skin diseases, such as psoriasis. SerpinB7 is identified as a skin-specific endogenous protease inhibitor, but the role and underlying mechanism in psoriasis are poorly understood. Here we found that SerpinB7 is highly expressed in psoriatic keratinocytes of patients and imiquimod-induced psoriatic lesions in mice. SerpinB7-/- mice showed abnormal epidermal barrier integrity and skin architecture in homeostasis, and aggravated psoriatic lesion with inhibiting terminal differentiation and increasing inflammatory cells infiltration compared to SerpinB7+/+ mice after Imiquimod treatment. Mechanistically, SerpinB7 deficiency results in excessive proliferation and impaired differentiation, as well as increased chemokines and antimicrobial peptide expression in normal human epidermal keratinocyte and mouse primary keratinocyte. Transcriptomics and proteomics results showed that the SeprinB7 deficiency affected keratinocyte differentiation and proinflammatory cytokines, possibly by affecting the calcium ion channel-related proteins. Notably, we demonstrated that SerpinB7 deficiency prevented the increase in intracellular Ca2+ influx, which was partly eliminated by the intracellular Ca2+ chelator BAPTA-AM. Our findings first described the critical role of SerpinB7 in the regulation of keratinocyte differentiation and psoriatic microenvironment mediated via keratinocytes' intracellular calcium flux, proposing a new candidate for therapeutic targets in psoriasis.

Investigating the Effects of IRF6 on Focal Adhesions in Keratinocytes

Focal adhesions are one of the two main types of adhesions between cells and the extra‐cellular matrix (ECM). Focal adhesions are dynamic complexes anchored to the actin cytoskeleton through intracellular adaptor proteins, and to the ECM through heterodimers of α and β integrins, forming a transmembrane link between the intra‐ and extra‐cellular space. β‐1 integrin is the primary β subunit found in keratinocytes, and its corresponding heterodimers show affinity for a wide range of ECM proteins including collagen, fibronectin, and laminin. Collagen is the main structural protein in cutaneous ECM (the dermis), while fibronectin is a glycoprotein found in the ECM that binds integrins and plays a crucial role in wound healing. Interferon regulatory factor 6 (IRF6) is a transcription factor expressed by epithelial cells that regulates keratinocyte differentiation, cell‐cell adhesions, and migration. It is well known that focal adhesions are required for cell migration, however the role of IRF6 in regulating focal adhesions is unknown. Therefore, we hypothesize that IRF6 regulates focal adhesion formation. To determine if IRF6 levels affect attachment to the ECM, we seeded wildtype and IRF6 knockdown keratinocytes on collagen IV and plastic and quantified the number of cells attached to the plate after thirty and sixty minutes. No differences were found between wild‐type and IRF6 knockdown keratinocytes on plastic. However, less IRF6 knockdown keratinocytes were attached on collagen IV compared to wildtypes. To explore how IRF6 affects focal adhesions, we plated IRF6 knockdown and wild‐type keratinocytes on different types of ECM that were representative of both normal and wounded conditions of the dermis. Immunofluorescent staining for β‐1 integrin and phalloidin was performed, followed by quantitative analysis of focal adhesion length and intensity. Initial observations indicate that IRF6 knockdown keratinocytes consistently have longer focal adhesions compared to the wildtype. Variations of β‐1 fluorescent intensity was also observed in wild‐type cells compared to IRF6 knockdown keratinocytes. These preliminary results suggest a role for IRF6 in regulating focal adhesions, providing a potential mechanism for the underlying defect observed in the migration of IRF6 deficient keratinocytes.

Thioredoxin-interacting protein regulates keratinocyte differentiation: Implication of its role in psoriasis.

Thioredoxin-interacting protein (TXNIP), also known as Vitamin-D upregulated protein-1 (VDUP-1), interacts with thioredoxin to regulate redox responses and participates in diverse disorders including metabolic, cardiovascular, inflammatory and malignant diseases. Psoriasis is characterized by chronic skin inflammation and an aberrant pattern of keratinocyte differentiation. Clinically, psoriasis is associated with various cardiometabolic comorbidities but studies on TXNIP's biological role in skin disorders are limited. In this study, we investigated TXNIP expression in psoriasis and its regulation in normal human epidermal keratinocytes (NHEKs), and then explored how TXNIP regulated skin keratinocyte differentiation to determine its role in psoriasis pathogenesis. Our immunohistochemical study demonstrated extensive TXNIP expression in the upper and lower epidermis of psoriasis compared to predominant TXNIP expression in the basal layer of normal skin. 1, 25-dihydroxyvitamin D3 suppressed but TGF-α and EGF enhanced TXNIP expression in NHEKs. An inducer of keratinocyte differentiation, phorbol 12-myristate 13-acetate (PMA), also diminished TXNIP expression, which was reversed by PKC-δ knockdown. TXNIP knockdown reduced PMA-induced involucrin and transglutaminse-1 expression, and increased p63 expression in NHEKs but did not significantly affect cell proliferation. H2 O2 -induced ROS production and EGFR phosphorylation decreased in NHEKs with TXNIP knockdown. Furthermore, PMA-induced PKC-δ phosphorylation, TGF-α, and EGF-triggered EGFR phosphorylation were attenuated by TXNIP knockdown. Our results unraveled the regulation and function of TXNIP expression in skin keratinocytes and the cross-regulation between TXNIP and EGFR signaling. These findings imply a role of TXNIP in psoriasis and provide insight into the possible impact of TXNIP regulators on the skin or psoriasis.

Spleen tyrosine kinase regulates keratinocyte inflammasome activation and skin inflammation induced by UVB irradiation

UVB can induce inflammatory responses contributing to diverse skin damage. UVB-triggered inflammasome activation of human keratinocytes underlies UVB-induced skin sunburn reaction. Pleiotropic functions of spleen tyrosine kinase (Syk) have rendered it as a potential therapeutic target. In immunocytes, Syk modulates immunoreceptor signaling and NLRP3 inflammasome activation. In skin, Syk mediates EGFR signaling, regulates keratinocyte differentiation and is involved in inflammatory disorders. However, roles of Syk in UVB-induced inflammasome activation in keratinocytes remain elusive. We investigated roles of keratinocyte Syk in UVB-triggered photo-responses. Primary normal human epidermal keratinocytes (NHEKs) isolated from skin were used. Syk knockdown or Syk inhibitor R406 was applied to investigate functions of keratinocyte Syk in UVB photobiology. The possible in vivo role of Syk was evaluated by checking UVB-induced skin damage in R406-treated mice. UVB was able to induce Syk phosphorylation in NHEKs that could be regulated by reactive oxygen species (ROS) generation and EGFR. Syk knockdown or Syk inhibitor (R406) treatment reduced UVB-triggered apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) crosslinking, procaspase-1 cleavage, active IL-1β formation, and gasdermin D activation, indicating roles of Syk in UVB-triggered inflammasome activation in keratinocytes. UVB-induced production of IL-8, TNF-α, ROS, and phosphorylation of JNK and p38 were attenuated after Syk knockdown or inhibition. R406 ameliorated UVB-induced mouse skin damage, including erythema and transepidermal water loss (TEWL). Thus, Syk participated in UVB-induced inflammasome activation and inflammatory response in vitro and in vivo, suggesting potential photo-protective effects of Syk inhibition in UVB-induced skin inflammation.

Leucosceptoside A from Devil's Claw Modulates Psoriasis-like Inflammation via Suppression of the PI3K/AKT Signaling Pathway in Keratinocytes.

Psoriasis is a chronic inflammatory skin condition characterized by abnormal keratinocyte proliferation and differentiation that is accompanied with dysregulated immune response and abnormal vascularization. Devil’s claw (Harpagophytum procumbens (Burch.) DC. ex Meisn.) tubers extract has been used both systemically and topically for treatment of chronic inflammatory diseases such as arthritis, osteoporosis, inflammatory bowel disease, among others. However, its potential mechanisms of action against psoriasis remains poorly investigated. The human keratinocyte HaCaT cell line is a well-accepted in vitro model system for inflammatory skin disorders such as psoriasis. The present study involved an exploration of the effect of biotechnologically produced H. procumbens (HP) cell suspension extract and pure phenylethanoid glycosides verbascoside (VER) and leucosceptoside A (LEU) in interferon (IFN)-γ/interleukin (IL)-17A/IL-22-stimulated HaCaT cells as a model of psoriasis-like inflammation. Changes in key inflammatory signaling pathways related to psoriasis development were detected by reverse transcription polymerase chain reaction and western blotting. Treatment with LEU, but not VER and HP extract improved psoriasis-related inflammation via suppression of the PI3K/AKT signaling in IFN-γ/IL-17A/IL-22-stimulated HaCaT cells. Our results suggest that LEU may exhibit therapeutic potential against psoriasis by regulating keratinocyte differentiation through inhibition of the PI3K/AKT pathway.

066 Single nucleotide polymorphisms in aldo-keto reductase 1C3 associate with early-onset psoriasis in female patients

Psoriasis is a multifactorial disease associated with both genetic and non-genetic factors. We hypothesized that single nucleotide polymorphisms (SNPs) in aldo-keto reductase (AKR) 1C3, which regulates keratinocyte differentiation and loricrin expression in human epidermis, confer a genetic susceptibility to psoriasis. In 232 psoriasis patients, including 171 males and 61 females, a TaqMan SNP genotyping assay revealed that the rs12529 genotype distribution in our cohort was G/G: 75.0%, G/C: 22.8%, and C/C: 2.2%, and the rs12387 genotype distribution was A/A: 75.0%, A/G: 22.8%, and G/G: 2.2%.

344 Identification of a novel skin-specific long non-coding RNA regulating keratinocyte differentiation

Long non-coding RNAs (lncRNAs) constitute an important layer of epigenetic control of gene expression. A few lncRNAs have been uncovered to regulate epidermal differentiation, a critical biological process in barrier maintenance and wound healing. Here, we report a novel skin-specific lncRNA, HOXC13-AS, that regulates keratinocyte differentiation by interacting with COPA (COPI Coat Complex Subunit Alpha) and further modulating endoplasmic reticulum (ER) stress. During human skin wound healing, epidermal cell-specific expression of HOXC13-AS was downregulated in the early phases but recovered to the intact skin level at day 30 after injuries.

105 Regulation of keratinocyte differentiation through aryl hydrocarbon receptor signaling involves the transient activation of TFAP2A

Terminal differentiation of keratinocytes is essential for skin barrier development and tightly coordinated by a complex network of interacting transcription factors. Previous work identified the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor and environmental sensor, to orchestrate epidermal differentiation through transient activation of putative downstream transcription factors, amongst others TFAP2A. For proof-of-concept studies on a presumed AHR- TFAP2A axis that is co-opted in epidermal differentiation, we utilized siRNA-mediated TFAP2A knockdown in primary keratinocytes and CRISPR-Cas9 induced TFAP2AKO in N/TERT keratinocytes combined with transcriptomic analysis and organotypic epidermis modeling.

Role of vitamin D in hair loss: A short review.

Vitamin D, a vitamin and hormone, plays an important role in dermatology and dermatotherapeutics, due to its anti-inflammatory and immunomodulatory properties, and regulation of keratinocyte differentiation and proliferation. It also affects the hair cycle, and its role in hair loss is under constant research. This review aims to give a brief overview of vitamin D biology within the hair follicle, role in the etiopathogenesis, and rationale for supplementation in various alopecias. A PubMed literature search was performed to review relevant current literature and studies investigating the role of vitamin D in the etiopathogenesis, as a supplement and a potential therapeutic modality in hair loss. Vitamin D is intricately involved in various signaling pathways of growth and differentiation of hair follicles. Most studies show an inverse relationship between serum vitamin D levels and non-scarring alopecias such as telogen effluvium, androgenetic alopecia, alopecia areata, and trichotillomania. Vitamin D deficiency is also associated with scarring alopecia. However, conclusive studies to demonstrate the benefit of vitamin D administration in correcting hair loss and managing these conditions are lacking. Hence, further studies are needed before vitamin D can be routinely recommended as a treatment modality in these conditions.