Keratinocyte Differentiation Markers Research Articles

Epidermal CD147 expression plays a key role in IL-22-induced psoriatic dermatitis

Psoriasis is a chronic inflammatory skin disease characterized by abnormal keratinocyte proliferation and terminal differentiation. Interleukin-22 (IL-22) and the transcription factor Stat3 play pivotal roles in the pathogenesis of psoriasis. CD147 is a transmembrane glycosylation protein that belongs to the immunoglobulin superfamily. Our previous studies have shown that CD147 is a marker of high keratinocyte proliferation and poor keratinocyte differentiation as well as a psoriasis susceptibility gene. The current study demonstrates that CD147 is highly expressed in psoriatic skin lesions. Specific CD147 over-expression in the epidermis of K5-promoter transgenic mice promotes imiquimod (IMQ)-induced psoriasis-like inflammation characterized by acanthosis, granular layer loss and inflammatory cell infiltration. We also found that IL-22 increases CD147 transcription in vitro and in vivo and that Stat3 binds directly to the CD147 promoter between positions −854 and −440, suggesting that CD147 expression is up-regulated in patients with psoriasis through Stat3 activation. In addition, CD147 knockdown dramatically blocks IL-22-mediated Stat3 activation as well as IL-22-induced cytokine, chemokine and antimicrobial factor expression. Together, these findings show that CD147 is a novel and key mediator of IL-22-induced psoriatic alterations in the epidermis and might be a therapeutic target in patients with psoriasis.

The effectiveness of epigallocathechin-3-gallate for treatment of human papillomavirus-driven epithelial neoplasms: a preclinical study

BackgroundEpigallocathechin-3-gallate (EGCG), the major bioactive polyphenol in green tea, has anticarcinogenic properties in vitro and in vivo. Several recent reports have shown that EGCG affects the expression of human papillomavirus (HPV)-encoded E6 and E7, two oncoproteins required for HPV-driven oncogenesis. Here, we aimed to explore the effects of EGCG on keratinocyte proliferation and differentiation, in addition to HPV18 replication, in a three-dimensional organotypic raft culture system. MethodsOrganotypic raft cultures of HPV18-infected keratinocytes cultured at the air–liquid interface for 10 days were treated with EGCG for an additional 10 days before fixation and processing. Raft sections were stained with antibodies specific for various cell proliferation and keratinocyte differentiation markers in addition to tumour suppressor genes. Western blotting was performed on EGCG-treated cells to measure the level of HPV18 E6 and E7 protein expression. FindingsEGCG treatment blocked the ability of HPV18-positive keratinocytes to generate hyperplastic epithelium in raft culture. EGCG reduced cell proliferation as assessed by bromodeoxyuridine label incorporation and Ki67 staining; it upregulated expression of several tumour suppressor genes (p53 [TP53], p21, pRb), and impaired productive viral replication (as assessed by HPV18 E4 protein expression), but did not have an effect on keratinocyte differentiation. In culture, EGCG treatment promoted degradation of the E6 and E7 proteins and restored tumour suppressor gene expression. InterpretationThe results of our preclinical study suggest that EGCG inhibits the proliferation of HPV18-infected keratinocytes by enhancing the turnover and degradation of the E6 and E7 proteins, resulting in re-expression of several key tumour suppressor genes. These findings suggest that EGCG could potentially reverse the dysplastic changes induced by oncogenic HPV strains and could be used clinically to treat HPV-induced neoplasia. FundingCancer Research UK.

Kinetin Improves Barrier Function of the Skin by Modulating Keratinocyte Differentiation Markers.

BackgroundKinetin is a plant hormone that regulates growth and differentiation. Keratinocytes, the basic building blocks of the epidermis, function in maintaining the skin barrier.ObjectiveWe examined whether kinetin induces skin barrier functions in vitro and in vivo.MethodsTo evaluate the efficacy of kinetin at the cellular level, expression of keratinocyte differentiation markers was assessed. Moreover, we examined the clinical efficacy of kinetin by evaluating skin moisture, transepidermal water loss (TEWL), and skin surface roughness in patients who used kinetin-containing cream. We performed quantitative real-time polymerase chain reaction to measure the expression of keratinocyte differentiation markers in HaCaT cells following treatment. A clinical trial was performed to assess skin moisture, TEWL, and evenness of skin texture in subjects who used kinetin-containing cream for 4 weeks.ResultsKinetin increased involucrin, and keratin 1 mRNA in HaCaT cells. Moreover, use of a kinetin-containing cream improved skin moisture and TEWL while decreasing roughness of skin texture.ConclusionKinetin induced the expression of keratinocyte differentiation markers, suggesting that it may affect differentiation to improve skin moisture content, TEWL, and other signs of skin aging. Therefore, kinetin is a potential new component for use in cosmetics as an anti-aging agent that improves the barrier function of skin.

MicroRNA-331-3p Suppresses Cervical Cancer Cell Proliferation and E6/E7 Expression by Targeting NRP2.

Aberrant expression of microRNAs (miRNAs) is involved in the development and progression of various types of cancers. In this study, we investigated the role of miR-331-3p in cell proliferation and the expression of keratinocyte differentiation markers of uterine cervical cancer cells. Moreover, we evaluated whether neuropilin 2 (NRP2) are putative target molecules that regulate the human papillomavirus (HPV) related oncoproteins E6 and E7. Cell proliferation in the human cervical cancer cell lines SKG-II, HCS-2, and HeLa was assessed using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay. Cellular apoptosis was measured using the TdT-mediated dUTP nick end labeling (TUNEL) and Annexin V assays. Quantitative RT-PCR was used to measure the messenger RNA (mRNA) expression of the NRP2, E6, E7, p63, and involucrin (IVL) genes. A functional assay for cell growth was performed using cell cycle analyses. Overexpression of miR-331-3p inhibited cell proliferation, and induced G2/M phase arrest and apoptosis in SKG-II, HCS-2 and HeLa cells. The luciferase reporter assay of the NRP2 3′-untranslated region revealed the direct regulation of NRP2 by miR-331-3p. Gene expression analyses using quantitative RT-PCR in SKG-II, HCS-2, and HeLa cells overexpressing miR-331-3p or suppressing NRP2 revealed down-regulation of E6, E7, and p63 mRNA and up-regulation of IVL mRNA. Moreover, miR-331-3p overexpression was suppressed NRP2 expression in protein level. We showed that miR-331-3p and NRP2 were key effectors of cell proliferation by regulating the cell cycle, apoptosis. NRP-2 also regulates the expression of E6/E7 and keratinocyte differentiation markers. Our findings suggest that miR-331-3p has an important role in regulating cervical cancer cell proliferation, and that miR-331-3p may contribute to keratinocyte differentiation through NRP2 suppression. miR-331-3p and NRP2 may contribute to anti-cancer effects.

Aryl hydrocarbon receptor negatively regulates lipid synthesis and involves in cell differentiation of SZ95 sebocytes in vitro

The aryl hydrocarbon receptor (AhR) is the receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), benzo(a)pyrene (BaP) and other exogenous compounds. In human sebocytes, TCDD and BaP were found to activate the expression of multiple genes, including cytochrome P450 1A1 (CYP1A1), and inhibit lipid synthesis via AhR, while little is known about endogenous functions of the AhR. In order to expand this knowledge, we analyzed the impact of AhR knockdown on lipid synthesis as well as on cell differentiation of SZ95 sebocytes in vitro and observed that lipid synthesis was significantly induced in AhR silenced SZ95 sebocytes. In line with this result, expression of lipogenesis-associated genes, such as peroxisome proliferator activated receptor (PPAR) δ and PPARγ, was increased. Morphological changes with smaller cells in size but more abundant cytoplasmic lipids were observed in AhR silenced SZ95 sebocytes compared with the AhR activated cells. Besides, the expression of keratin 7, an early sebaceous differentiation marker, was increased, while the expression of the terminal sebocyte differentiation marker epithelial membrane antigen (EMA) was reduced. Moreover, the terminal keratinocyte differentiation markers keratin 10 and involucrin, and the AhR downstream protein CYP1A1 were reduced after AhR silencing. To the best of our knowledge, we provide evidence that in the absence of exogenous ligands, the AhR inhibits lipid synthesis and involves in cell differentiation of human SZ95 sebocytes, which indicates the physiological function of this receptor in human sebocytes.

Ingenol Disoxate: A Novel 4-Isoxazolecarboxylate Ester of Ingenol with Improved Properties for Treatment of Actinic Keratosis and Other Non-Melanoma Skin Cancers.

IntroductionIngenol mebutate gel (Picato®, LEO Pharma A/S) is approved for the field treatment of actinic keratosis and is characterized by high sustained clearance of actinic lesions. The inherent propensity of ingenol mebutate towards chemical rearrangement necessitates refrigeration of the final product. We sought to identify novel ingenol derivatives with enhanced chemical stability and similar or improved in vitro potency and in vivo efficacy.MethodsA number of ingenol esters were synthesized with full regiocontrol from ingenol. Chemical stability was determined in aqueous buffer at physiological pH and hydroalcoholic gel at lower pH. Acute cytotoxicity was determined in HeLa or HSC-5 cells. Keratinocyte proliferation, viability and caspase 3/7 activation was measured in primary epidermal keratinocytes. Relative gene expression levels were determined by real-time quantitative PCR. Evaluation of in vivo tumor ablating potential was performed in the murine B16 melanoma mouse model and in the UV-induced skin carcinogenesis model in hairless SKH-1 mice following topical treatment for two consecutive days with test compounds formulated at 0.1% in a hydroalcoholic gel.ResultsThis work resulted in the identification of ingenol disoxate (LEO 43204) displaying increased stability in a clinically relevant formulation and in aqueous buffer with minimal pH-dependent acyl migration degradation. Ingenol disoxate exhibited a significantly higher cytotoxic potency relative to ingenol mebutate. Likewise, cell growth arrest in normal human keratinocyte was more potently induced by ingenol disoxate, which was accompanied by protein kinase C dependent transcription of markers of keratinocyte differentiation. Most notably, ingenol disoxate possessed a superior antitumor effect in a B16 mouse melanoma model and significantly increased median survival time relative to ingenol mebutate. A significant effect on tumor ablation was also observed in a murine model of ultraviolet irradiation-induced skin carcinogenesis.ConclusionThese data illustrate that the favorable in vitro and in vivo pharmacological properties driving ingenol mebutate efficacy are either preserved or improved in ingenol disoxate. In combination with improved chemical stability to potentially facilitate storage of the final product at ambient temperatures, these features support further development of ingenol disoxate as a convenient and efficacious treatment modality of non-melanoma skin cancers.FundingLEO Pharma A/S.Electronic supplementary materialThe online version of this article (doi:10.1007/s13555-016-0137-2) contains supplementary material, which is available to authorized users.

Bcl11b/Ctip2 is required for development of lingual papillae in mice

Molecular mechanisms underlying the development and morphogenesis of oral epithelia, comprising the gustatory and nongustatory epithelium, remain unclear. Here, we show that Bcl11b, a zinc finger transcription factor, plays an important role in the development of lingual papillae, especially filiform papillae. In both gustatory and nongustatory epithelium, Bcl11b was expressed in keratin 14–positive epithelial basal cells, which differentiate into keratinocytes and/or taste cells. Loss of Bcl11b function resulted in abnormal morphology of the gustatory papillae: flattened fungiform papillae, shorter trench wall in the foliate and circumvallate papillae, and ectopic invagination in more than half of circumvallate papillae. However, Bcl11b loss caused no effect on differentiation of taste receptor cells. In nongustatory epithelium, the impact of Bcl11b deficiency was much more striking, resulting in a smooth surface on the tongue tip and hypoplastic filiform papillae in the dorsal lingual epithelium. Immunohistochemical analyses revealed that a keratinocyte differentiation marker, Tchh expression was severely decreased in the Bcl11b−/− filiform papillae. In addition, expression of Pax9, required for morphogenesis of filiform papillae and its downstream target genes, hard keratins, almost disappeared in the tongue tip and was decreased in the dorsal tongue of Bcl11b−/− mice. Gene expression analyses demonstrated a delayed onset of expression of epithelial differentiation complex genes, which disturbed barrier formation in the mutant tongue. These results indicate that Bcl11b regulates the differentiation of keratinocytes in the tongue and identify Bcl11b as an essential factor for the lingual papilla morphogenesis.

Phosphoprotein Phosphatase 1 Is Required for Extracellular Calcium-Induced Keratinocyte Differentiation.

Extracellular calcium is a major regulator of keratinocyte differentiation in vitro and appears to play that role in vivo, but the mechanism is unclear. We have previously demonstrated that, following calcium stimulation, PIP5K1α is recruited by the E-cadherin-β-catenin complex to the plasma membrane where it provides the substrate PIP2 for both PI3K and PLC-γ1. This signaling pathway is critical for calcium-induced generation of second messengers including IP3 and intracellular calcium and keratinocyte differentiation. In this study, we explored the upstream regulatory mechanism by which calcium activates PIP5K1α and the role of this activation in calcium-induced keratinocyte differentiation. We found that treatment of human keratinocytes in culture with calcium resulted in an increase in serine dephosphorylation and PIP5K1α activation. PP1 knockdown blocked extracellular calcium-induced increase in serine dephosphorylation and activity of PIP5K1α and induction of keratinocyte differentiation markers. Knockdown of PLC-γ1, the downstream effector of PIP5K1α, blocked upstream dephosphorylation and PIP5K1α activation induced by calcium. Coimmunoprecipitation revealed calcium induced recruitment of PP1 to the E-cadherin-catenin-PIP5K1α complex in the plasma membrane. These results indicate that PP1 is recruited to the extracellular calcium-dependent E-cadherin-catenin-PIP5K1α complex in the plasma membrane to activate PIP5K1α, which is required for PLC-γ1 activation leading to keratinocyte differentiation.

Hypoxia-mediated activation of autophagic flux inhibits apoptosis of keratinocytes via blocking tumor necrosis factor-related apoptosis-inducing ligand

Tumor necrosis factor‑related apoptosis‑inducing ligand (TRAIL) is toxic against transformed tumor cells. Cornification is the terminal differentiation of keratinocytes and a specific form of programmed cell death caused by TRAIL that occurs in keratinocytes. Apoptosis can also be triggered when TRAIL induces expression of keratinocyte differentiation markers. The present study reported that hypoxia inhibits TRAIL‑induced apoptosis due to autophagic flux. It is well known that hypoxia activates autophagy in keratinocytes and reduces p62 protein levels. The present study demonstrated that hypoxia inhibited TRAIL‑mediated apoptosis and induced autophagic flux in HaCaT cells. In addition, autophagic flux‑inactivating reagents, including 3‑methyladenine and chloroquine, increased the TRAIL sensitivity of HaCaT cells exposed to hypoxia. In conclusion, these results indicated that inactivating autophagy increased TRAIL sensitivity in hypoxic HaCaT cells. Autophagy inhibitors may be beneficial in therapies using TRAIL against skin cancers.

Pharmacological activation of estrogen receptors-α and-β differentially modulates keratinocyte differentiation with functional impact on wound healing.

Estrogen deprivation is considered responsible for many age-related processes, including poor wound healing. Guided by previous observations that estradiol accelerates re-epithelialization through estrogen receptor (ER)-β, in the present study, we examined whether selective ER agonists [4,4′,4″-(4-propyl [1H] pyrazole-1,3,5-triyl)-trisphenol (PPT), ER-α agonist; 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN), ER-β agonist] affect the expression of basic proliferation and differentiation markers (Ki-67, keratin-10, -14 and -19, galectin-1 and Sox-2) of keratinocytes using HaCaT cells. In parallel, ovariectomized rats were treated daily with an ER modulator, and wound tissue was removed 21 days after wounding and routinely processed for basic histological analysis. Our results revealed that the HaCaT keratinocytes expressed both ER-α and -β, and thus are well-suited for studying the effects of ER agonists on epidermal regeneration. The activation of ER-α produced a protein expression pattern similar to that observed in the control culture, with a moderate expression of Ki-67 being observed. However, the activation of ER-β led to an increase in cell proliferation and keratin-19 expression, as well as a decrease in galectin-1 expression. Fittingly, in rat wounds treated with the ER-β agonist (DPN), epidermal regeneration was accelerated. In the present study, we provide information on the mechanisms through which estrogens affect the expression patterns of selected markers, thus modulating keratinocyte proliferation and differentiation; in addition, we demonstrate that the pharmacological activation of ER-α and -β has a direct impact on wound healing.

S100A16 promotes differentiation and contributes to a less aggressive tumor phenotype in oral squamous cell carcinoma

BackgroundAltered expression of S100A16 has been reported in human cancers, but its biological role in tumorigenesis is not fully understood. This study aimed to investigate the clinical significance and functional role of S100A16 in oral squamous cell carcinoma (OSCC) suppression.MethodsS100A16 mRNA and/or protein levels were examined by quantitative RT-PCR and immunohistochemistry in whole- and laser microdissected-specimens of normal human oral mucosa (NHOM, n = 65), oral dysplastic lesions (ODL, n = 21), OSCCs (n = 132) and positive cervical nodes (n = 17). S100A16 protein expression in OSCC was examined for correlations with clinicopathological variables and patient survival. S100A16 was over-expressed and knocked-down in OSCC-derived (CaLH3 and H357) cells by employing retroviral constructs to investigate its effects on cell proliferation, sphere formation and three dimensional (3D)-organotypic invasive abilities in vitro and tumorigenesis in a mouse xenograft model.ResultsBoth S100A16 mRNA and protein levels were found to be progressively down-regulated from NHOM to ODL and OSCC. Low S100A16 protein levels in OSCC significantly correlated with reduced 10-year overall survival and poor tumor differentiation. Analysis of two external OSCC microarray datasets showed a positive correlation between the mRNA expression levels of S100A16 and keratinocyte differentiation markers. CaLH3 and H357 cell fractions enriched for differentiated cells either by lack of adherence to collagen IV or FACS sorting for low p75NTR expression expressed significantly higher S100A16 mRNA levels than the subpopulations enriched for less differentiated cells. Corroborating these findings, retroviral mediated S100A16 over-expression and knock-down in CaLH3 and H357 cells led to respective up- and down-regulation of differentiation markers. In vitro functional studies showed significant reduction in cell proliferation, sphere formation and 3D-invasive abilities of CaLH3 and H357 cells upon S100A16 over-expression. These functional effects were associated with concomitant down-regulation of self-renewal (Bmi-1 and Oct 4A) and invasion related (MMP1 and MMP9) molecules. S100A16 over-expression also suppressed tumorigenesis of H357 cells in a mouse xenograft model and the resulting tumor xenografts displayed features/expression of increased differentiation and reduced proliferation/self-renewal.ConclusionsThese results indicate that S100A16 is a differentiation promoting protein and might function as a tumor suppressor in OSCC.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1622-1) contains supplementary material, which is available to authorized users.

A chemically defined culture medium containing Rho kinase inhibitor Y-27632 for the fabrication of stratified squamous epithelial cell grafts

With the development of a culture method for stratified squamous epithelial cells, tissue-engineered epithelial cell sheets have been successfully applied as clinical cell grafts. However, the implementation of these cell sheets without the use of any animal-derived materials is highly desirable. In this study, Rho-associated protein kinase inhibitor Y-27632 was used to develop a chemically defined culture medium for the fabrication of stratified epithelial cell grafts consisting of human epidermal and oral keratinocytes, and the proliferation activity, cell morphology, and gene expressions of the keratinocytes were analyzed. The results of a colorimetric assay indicated that Y-27632 significantly promoted the proliferation of the keratinocytes in culture media both with and without fetal bovine serum (FBS), although there were no indications of Y-27632 efficacy on cell morphology and stratification of the keratinocytes in culture medium without any animal-derived materials. The results of quantitative RT-PCR revealed that gene expressions correlated with cell adhesion, cell–cell junction, proliferation markers, and stem/progenitor markers in cultured keratinocytes were not strongly affected by the addition of Y-27632 to the culture medium. Moreover, gene expressions of differentiation markers in stratified keratinocytes cultured in medium without FBS were nearly identical to those of keratinocytes co-cultured with 3T3 feeder cells. Interestingly, the expressions of differentiation markers in cultured stratified keratinocytes were suppressed by FBS, whereas they were reconstructed by either co-culture of a 3T3 feeder layer or addition of Y-27632 into the culture medium containing FBS. These findings indicate that Y-27632 is a useful supplement for the development of a chemically defined culture medium for fabrication of stratified epithelial cell grafts for clinical applications for the purpose of developing the culture medium with a lower risk of pathogen transmission that might arise from animal-derived materials.

The antipsoriatic agent monomethylfumarate has antiproliferative, prodifferentiative, and anti-inflammatory effects on keratinocytes.

Monomethylfumarate (MMF) is thought to be the bioactive ingredient of the drug Fumaderm (Biogen Idec, Cambridge, MA), licensed in Germany since 1994 for the treatment of moderate-to-severe psoriasis. Psoriasis is a common inflammatory hyperproliferative skin disorder that involves cross-talk between different cell types, including immune cells and keratinocytes. Psoriatic lesions are characterized by hyperproliferation, aberrant differentiation, and inflammation, with the psoriatic cytokine network maintained by communication between immune cells and keratinocytes. Recently, there is increasing evidence regarding the pivotal role of keratinocytes in mediating the disease process, and these cells can be regarded as safe therapeutic targets. From the data available on human subjects treated with Fumaderm, MMF is an effective antipsoriatic agent with known effects on immune cells. However, little is known about its direct effects on keratinocytes. We hypothesized that MMF has direct antiproliferative, prodifferentiative, and anti-inflammatory effects on keratinocytes. Indeed, MMF dose-dependently inhibited [(3)H]thymidine incorporation into DNA, indicating a direct antiproliferative action on keratinocytes. MMF significantly increased the protein level of keratin 10, the early keratinocyte differentiation marker, and the activity of transglutaminase, a late differentiation marker. These results are consistent with an ability of MMF to promote keratinocyte differentiation and inhibit proliferation, thereby improving psoriatic lesions. In 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced keratinocytes, MMF significantly inhibited the expression of the proinflammatory cytokines, tumor necrosis factor-α (TNFα), interleukin-6, and interleukin-1α as well as the production of TNFα. Our results support the notion that MMF has direct antiproliferative, prodifferentiative, and anti-inflammatory effects on keratinocytes, highlighting its potential use as a multifactorial antipsoriatic agent.

The antimicrobial protein S100A7/psoriasin enhances the expression of keratinocyte differentiation markers and strengthens the skin's tight junction barrier.

S100A7/psoriasin is a member of the S100 protein family and is encoded in the epidermal differentiation complex, which contains genes for markers of epidermal differentiation. S100A7/psoriasin is overexpressed in hyperproliferative skin diseases, where it is believed not only to exhibit antimicrobial functions, but also to induce immunomodulatory activities, including chemotaxis and cytokine/chemokine production. To evaluate the effect of S100A7/psoriasin on keratinocyte differentiation and regulation of the tight junction (TJ) barrier. Expression of differentiation markers and TJ proteins in human keratinocytes was determined by real-time polymerase chain reaction and Western blot. The changes in TJ barrier function were assessed by transepithelial electrical resistance and paracellular permeability assays. Glycogen synthase kinase-3 (GSK-3) and mitogen-activated protein kinase (MAPK) activation was analysed by Western blot, whereas β-catenin and E-cadherin activation was evaluated by Western blot and immunofluorescence. S100A7/psoriasin enhanced the expression of several differentiation markers and selectively increased the expression of TJ proteins (e.g. claudins and occludin), which are known to strengthen the TJ barrier. Furthermore, S100A7/psoriasin increased β-catenin and E-cadherin accumulation at cell-cell contact, and enhanced transepithelial electrical resistance while reducing the paracellular permeability of keratinocyte layers. The data suggest that S100A7/psoriasin-mediated regulation of the TJ barrier was via both the GSK-3 and MAPK pathways, as evidenced by the inhibitory effects of inhibitors for GSK-3 and MAPKs. Our finding that S100A7/psoriasin regulates differentiation and strengthens TJ barrier function provides novel evidence that, in addition to antimicrobial and immunoregulatory activities, S100A7/psoriasin is involved in skin innate immunity.

SIRT2 as a new player in epigenetic programming of keratinocyte differentiation and a candidate tumor suppressor.

Epidermal keratinocytes undergo a continuous process of terminal differentiation, which is accompanied by a dramatic change in the expression and composition of keratins. This complex and carefully orchestrated process is regulated by a large number of signal transduction events and transcriptional factors as well as by epigenetic regulatory mechanisms, namely by histone methylation/acetylation and DNA methylation. In a recent issue of Exp Dermatol, Ming etal. provide evidence that sirtuin-2 (SIRT2), a NAD+-dependent deacetylase, inhibits the expression of keratin 15 and keratin 19, epidermal stem cell markers, while it stimulates the expression of loricrin, a marker of terminal keratinocyte differentiation. Human skin cancer cells show downregulation of SIRT2, and its deletion increases tumor growth in mice. Overall, these findings suggest that this deacetylase is involved in the epigenetic regulation of keratinocyte differentiation and exerts intracutaneous tumor suppressor functions.

Insulin-transferrin-selenium as an alternative to foetal serum for epidermal equivalents.

Organotypic skin models are powerful tools for research in development, ageing and diseases. They have become more and more complex with the use of multiple cell types. This requires a culture medium adapted to optimize the development of such in vitro skin. Foetal bovine serum (FBS) is the most complete supplement in existence at the moment, providing at once growth factors, vitamins, hormones and other circulating compounds. However, this cocktail suffers from batch variability and its animal origin is ethically questionable. More importantly, its biological activities may interfere with the study of certain signalling pathways. Here, we present a strategy for constructing an epidermal equivalent using a defined culture medium without serum. An epidermal equivalent was constructed with primary human keratinocytes cultured using an insulin-transferrin-selenium (ITS) medium. Determination of steady-state gene expression levels and the immunohistological characterization of keratinocyte markers were performed to compare the ITS medium condition with a reference model, where keratinocytes were co-cultured with fibroblasts in the presence of FBS. The data show that the ITS medium promoted the expression of keratinocyte proliferation and differentiation markers at the protein and transcript levels in a similar way to that of the reference model. We show that culture using the ITS medium appears as a viable replacement for FBS in the construction of epidermal equivalents, opening the way to signal transduction studies.

Inhibition of keratinocyte differentiation by the synergistic effect of IL-17A, IL-22, IL-1α, TNFα and oncostatin M.

Keratinocyte differentiation program leading to an organized epidermis plays a key role in maintaining the first line of defense of the skin. Epidermal integrity is regulated by a tight communication between keratinocytes and leucocytes, particularly under cytokine control. Imbalance of the cytokine network leads to inflammatory diseases such as psoriasis. Our attempt to model skin inflammation showed that the combination of IL-17A, IL-22, IL-1α, OSM and TNFα (Mix M5) synergistically increases chemokine and antimicrobial-peptide expression, recapitulating some features of psoriasis. Other characteristics of psoriasis are acanthosis and down-regulation of keratinocyte differentiation markers. Our aim was to characterize the specific roles of these cytokines on keratinocyte differentiation, and to compare with psoriatic lesion features. All cytokines decrease keratinocyte differentiation markers, but IL-22 and OSM were the most powerful, and the M5 strongly synergized the effects. In addition, IL-22 and OSM induced epidermal hyperplasia in vitro and M5 induced epidermal thickening and decreased differentiation marker expression in a mouse model, as observed in human psoriatic skin lesions. This study highlights the precise role of cytokines in the skin inflammatory response. IL-22 and OSM more specifically drive epidermal hyperplasia and differentiation loss while IL-1α, IL-17A and TNFα were more involved in the activation of innate immunity.

Keratinocyte detachment-differentiation connection revisited, or anoikis-pityriasi nexus redux.

Epidermis, a continuously self-renewing and differentiating organ, produces a protective stratum corneum that shields us from external chemical, physical and microbial threats. Epidermal differentiation is a multi-step process regulated by influences, some unknown, others insufficiently explored. Detachment of keratinocytes from the basement membrane is one such pro-differentiation stimulus. Here, we define the transcriptional changes during differentiation, especially those caused by detachment from the substratum. Using comprehensive transcriptional profiling, we revisited the effects of detachment as a differentiation signal to keratinocytes. We identified the genes regulated by detachment, the corresponding ontological categories and, using metaanalysis, compared the genes and categories to those regulated by other pro-differentiating stimuli. We identified 762 genes overexpressed in suspended keratinocyte, including known and novel differentiation markers, and 1427 in attached cells, including basal layer markers. Detachment induced epidermis development, cornification and desmosomal genes, but also innate immunity, proliferation inhibitors, transcription regulators and MAPKs; conversely the attached cells overexpressed cell cycle, anchoring, motility, splicing and mitochondrial genes, and both positive and negative regulators of apoptosis. Metaanalysis identified which detachment-regulated categories overlap with those induced by suprabasal location in vivo, by reaching confluency in vitro, and by inhibition of JUN kinases. Attached and in vivo basal cells shared overexpression of mitochondrial components. Interestingly, melanosome trafficking components were also overexpressed in the attached and in vivo basal keratinocytes. These results suggest that specific pro-differentiation signals induce specific features of the keratinization process, which are in vivo orchestrated into harmonious epidermal homeostasis.

Effects of low molecular weight soybean peptide on mRNA and protein expression levels of differentiation markers in normal human epidermal keratinocytes.

Low molecular weight soybean peptide (LSP) was applied to normal human epidermal keratinocytes, and the results showed a significant increase in the gene expression levels of involucrin, transglutaminase, and profilaggrin. Filaggrin protein levels were also significantly higher. It is possible that LSP has an epidermal cell differentiation-promoting effect and may be able to regulate metabolism of the epidermis.

Epigallocatechin-3-O-(3-O-methyl)-gallate-induced Differentiation of Human Keratinocytes Involves Klotho-Mediated Regulation of Protein Kinase-cAMP Responsive Element-Binding Protein Signaling

(−)-Epigallocatechin-3-O-gallate (EGCG) has long been known as a potent inducer of keratinocyte differentiation. Although its molecular mechanisms have been extensively studied, its actions on human skin remain to be elucidated. In this study, we demonstrated that methylated EGCG and EGCG increase the expression of klotho, and that klotho functions as a downstream target of EGCG and methylated EGCG in keratinocyte differentiation. We demonstrated that methylated EGCG3 and EGCG induce morphological changes in normal human epidermal keratinocytes (NHEKs) that are related to up-regulation of klotho expression. We also demonstrated that a klotho-induced keratinocyte differentiation marker in NHEKs is inhibited by H-89, a protein kinase (PKA) inhibitor. These results suggest that methylated EGCG and EGCG may function as inducers of keratinocyte differentiation via transcriptional regulation of the klotho protein.