Reconstructed human epidermis for in vitro studies on atopic dermatitis: A review

Different immortalized keratinocyte cell lines display distinct capabilities to differentiate and reconstitute an epidermis in vitro

Dermatological research relies on the availability of suitable models that most accurately reflect the in vivo situation. Primary keratinocytes obtained from skin reduction surgeries are not only limited by availability but have a short lifespan and show donor-specific variations, which hamper the understanding of general mechanisms. The spontaneously immortalized keratinocyte cell line HaCaT displays chromosomal aberrations and is known to differentiate in an abnormal manner. To overcome these issues, we validated different engineered immortalized cell lines created from primary human keratinocytes (NHK) as model systems to study epidermal function. Cell lines either immortalized by the expression of SV40 large T antigen and hTERT (NHK-SV/TERT) or by transduction with HPV E6/E7 (NHK-E6/E7) were analysed for their growth and differentiation behaviour using 2D and 3D culture systems and compared to primary keratinocytes. Both cell lines displayed a robust proliferative behaviour but were still sensitive to contact inhibition. NHK-E6/E7 could be driven into differentiation by Ca2+ switch, while NHK-SV/TERT needed withdrawal from any proliferative signal to initiate a delayed onset of differentiation. In 3D epidermal models both cell lines were able to reconstitute a stratified epidermis and functional epidermal barrier. However, only NHK-E6/E7 showed a degree of epidermal maturation and stratification that was comparable to primary keratinocytes.

Effects of Histamine and the α-Tocopherol Metabolite α-13'-COOH in an Atopic Dermatitis Full-Thickness Skin Model

Atopic dermatitis is a T-cell mediated inflammatory skin disease with detected elevated levels of histamine in skin or plasma. In this study, the effects of histamine in a T_H2 cytokine environment on human keratinocytes and three-dimensional skin models were investigated. These models were used to explore the anti-inflammatory properties of the α-tocopherol-derived long-chain metabolite α-13'-carboxychromanol (α-13'-COOH). Histamine and T_H2 cytokine-induced proliferation of keratinocytes was studied using a scratch assay. The inflammatory marker interleukin-8 was significantly increased in healthy and T_H2 cytokine-stimulated keratinocytes and skin models after histamine treatment. The incubation of full-thickness skin models with T_H2 cytokines and histamine resulted in morphological changes in the epidermal layer, interpreted as hyperkeratosis. α-13'-COOH significantly decreased interleukin-8 in these disease-associated skin models. Histological staining of filaggrin showed skin-strengthening effects following α-13'-COOH treatment, without changes in mRNA expression. Cytokeratin 10 mRNA expression tended to be increased in response to α-13'-COOH. Anti-allergic properties of α-13'-COOH were studied by pre-incubation of human leukocytes with α-13'-COOH. This resulted in reduced sulfido-leukotriene synthesis. The hyperproliferation effect of histamine in atopic dermatitis skin models may be of further interest to the study of disease-associated morphological changes. Moreover, α-13'-COOH is a promising natural compound for the treatment of inflammatory skin diseases.

Involvement of hypoxia-inducible factor activity in inevitable air-exposure treatment upon differentiation in a three-dimensional keratinocyte culture

Formation of the human skin epidermis can be reproduced by a three-dimensional (3D) keratinocyte culture system, in which air-exposure is inevitable upon initiation of differentiation. In the continuous submerged culture without air-exposure, even with a differentiation-compatible medium, several keratinocyte-specific proteins were not induced resulting in the formation of aberrant epidermal layers. To clarify the mechanism by which air-exposure promotes keratinocyte differentiation, we performed a comparative analysis on biological properties between submerged and air-liquid interphase culture systems. By transcriptomic analysis, hypoxia-inducible factor (HIF)-related genes appeared to significantly change in these cultured cells. In submerged culture, the transcriptional activity of HIF on its canonical response element was enhanced, while air-exposure treatment drastically reduced the transcriptional activity despite the high HIF protein level. Regulating HIF activity through reagents and genetic manipulation revealed that the reduced but retained HIF-transcriptional activity was essentially involved in differentiation. Furthermore, we showed, for the first time, that artificial supplementation of oxygen in the submerged culture system could restore keratinocyte differentiation as observed in the air-exposed culture. Thus, we mechanistically evaluated how HIF regulates the air-exposure-dependent differentiation of keratinocytes in a 3D culture system.

An Interleukin-4 and Interleukin-13 Induced Atopic Dermatitis Human Skin Equivalent Model by a Skin-On-A-Chip

Currently, the mechanism of progression of atopic dermatitis (AD) is not well understood because there is no physiologically appropriate disease model in terms of disease complexity and multifactoriality. Type 2 inflammation, mediated by interleukin (IL)-4 and IL-13, plays an important role in AD. In this study, full-thickness human skin equivalents consisting of human-derived cells were fabricated from pumpless microfluidic chips and stimulated with IL-4 and IL-13. The morphological properties, gene expression, cytokine secretion and protein expression of the stimulated human skin equivalent (HSE) epidermis were investigated. The results showed epidermal and spongy formations similar to those observed in lesions in AD, and decreased expression of barrier-related filaggrin, loricrin and involucrin genes and proteins induced by IL-4Rα signaling. In addition, we induced the expression of carbonic anhydrase II (CAII), a gene specifically expressed in the epidermis of patients with AD. Thus, AD human skin equivalents can be used to mimic the key pathological features of atopic dermatitis, overcoming the limitations of existing studies that rely solely on mouse models and have been unable to translate their effects to humans. Our results will be useful for future research on the development of therapeutic agents for atopic dermatitis.

Assessment of skin inflammation using near-infrared Raman spectroscopy combined with artificial intelligence analysis in an animal model

Near-infrared (NIR) Raman spectroscopy was applied to detect skin inflammation in an animal model. Artificial intelligence (AI) analysis improved prediction accuracy for skin inflammation.

Epidermal Hyaluronan in Barrier Alteration-Related Disease

In skin, although the extracellular matrix (ECM) is highly developed in dermis and hypodermis, discrete intercellular spaces between cells of the living epidermal layers are also filled with ECM components. Herein, we review knowledge about structure, localization and role of epidermal hyaluronan (HA), a key ECM molecule. HA is a non-sulfated glycosaminoglycan non-covalently bound to proteins or lipids. Components of the basal lamina maintain some segregation between the epidermis and the underlying dermis, and all epidermal HA is locally synthesized and degraded. Functions of HA in keratinocyte proliferation and differentiation are still controversial. However, through interactions with partners, such as the TSG-6 protein, HA is involved in the formation, organization and stabilization of the epidermal ECM. In addition, epidermal HA is involved in the formation of an efficient epidermal barrier made of cornified keratinocytes. In atopic dermatitis (AD) with profuse alterations of the epidermal barrier, HA is produced in larger amounts by keratinocytes than in normal skin. Epidermal HA inside AD lesional skin is located in enlarged intercellular spaces, likely as the result of disease-related modifications of HA metabolism.

Validation study of a new reconstructed human epidermis model EPiTRI for in vitro skin irritation test according to OECD guidelines

Following the global trend of reducing animal testing, various reconstructed human epidermis (RHE) models for skin irritation test (SIT) have been developed, verified, validated and included in OECD TG 439. We developed a new RHE called EPiTRI and a SIT method using EPiTRI (EPiTRI-SIT model) following the OECD guidelines. EPiTRI possesses morphological, biochemical and physiological properties similar to human epidermis with well-differentiated multilayered viable cells with barrier function. The EPiTRI-SIT model was tested for 20 reference chemicals in Performance Standard of OECD TG 439 (GD 220), showing good predictive capacity with 100% sensitivity, 70% specificity and 85% accuracy. EPiTRI had sensitivity in detecting di-n-propyl disulphate, as an irritant chemical (UN GHS Category 2), whereas most validated reference methods detected it as a non-irritant. An international validation study of EPiTRI-SIT was conducted in four laboratories to confirm the within- and between-laboratory reproducibility, as well as predictive capacity. The phase I/II within-laboratory and between-laboratory reproducibility was 100%/95% and 95%, respectively. The overall sensitivity, specificity and accuracy of EPiTRI-SIT was 96%, 70% and 83%, respectively, which fulfilled the OECD criteria. Thus, EPiTRI, meets the criteria of Performance Standards of OECD TG 439 (GD 220) and is suitable for screening irritating chemicals in vitro.

Polymer-Based Smart Drug Delivery Systems for Skin Application and Demonstration of Stimuli-Responsiveness

Progress in recent years in the field of stimuli-responsive polymers, whose properties change depending on the intensity of a signal, permitted an increase in smart drug delivery systems (SDDS). SDDS have attracted the attention of the scientific community because they can help meet two current challenges of the pharmaceutical industry: targeted drug delivery and personalized medicine. Controlled release of the active ingredient can be achieved through various stimuli, among which are temperature, pH, redox potential or even enzymes. SDDS, hitherto explored mainly in oncology, are now developed in the fields of dermatology and cosmetics. They are mostly hydrogels or nanosystems, and the most-used stimuli are pH and temperature. This review offers an overview of polymer-based SDDS developed to trigger the release of active ingredients intended to treat skin conditions or pathologies. The methods used to attest to stimuli-responsiveness in vitro, ex vivo and in vivo are discussed.

Influence of silymarin components on keratinocytes and 3D reconstructed epidermis

Silymarin is a flavonoid complex isolated from the plant Silybum marianum which is well known for its antioxidant, hepatoprotective and immunomodulatory effects. Since little is known about its anti-inflammatory properties and healing effects, our study focused on whether or not silymarin components reduce inflammation and support epidermis regeneration. Lipopolysaccharides (LPS) and sodium dodecyl sulfate (SDS) were used to induce inflammation in normal human epidermal keratinocytes (NHEKs) and reconstructed epidermis (RHE), respectively. The expression of pro-inflammatory cytokines (IL-1, IL-6 and IL-8) in NHEKs and RHE was measured by enzyme - linked immunosorbent assay (ELISA). The expression of cytokeratin 14 and loricrin in RHE was detected by immunofluorescent analysis. Hematoxylin and eosin staining was used for the morphological evaluation of RHE. It was determined that 2, 3 - dehydrosilybin (DHSB) downregulated the production of selected pro-inflammatory cytokines produced by NHEKs. Although all layers of RHE displayed full thickness, when SDS was applied, cell detachment was seen in the stratum corneum and loricrin expression was diminished.

Utilization of patterned bioprinting for heterogeneous and physiologically representative reconstructed epidermal skin models

Organotypic skin tissue models have decades of use for basic research applications, the treatment of burns, and for efficacy/safety evaluation studies. The complex and heterogeneous nature of native human skin however creates difficulties for the construction of physiologically comparable organotypic models. Within the present study, we utilized bioprinting technology for the controlled deposition of separate keratinocyte subpopulations to create a reconstructed epidermis with two distinct halves in a single insert, each comprised of a different keratinocyte sub-population, in order to better model heterogonous skin and reduce inter-sample variability. As an initial proof-of-concept, we created a patterned epidermal skin model using GPF positive and negative keratinocyte subpopulations, both printed into 2 halves of a reconstructed skin insert, demonstrating the feasibility of this approach. We then demonstrated the physiological relevance of this bioprinting technique by generating a heterogeneous model comprised of dual keratinocyte population with either normal or low filaggrin expression. The resultant model exhibited a well-organized epidermal structure with each half possessing the phenotypic characteristics of its constituent cells, indicative of a successful and stable tissue reconstruction. This patterned skin model aims to mimic the edge of lesions as seen in atopic dermatitis or ichthyosis vulgaris, while the use of two populations within a single insert allows for paired statistics in evaluation studies, likely increasing study statistical power and reducing the number of models required per study. This is the first report of human patterned epidermal model using a predefined bioprinted designs, and demonstrates the relevance of bioprinting to faithfully reproduce human skin microanatomy.

Skin irritation and inhalation toxicity of biocides evaluated with reconstructed human epidermis and airway models

Biocides are widely used in household products. Humans are exposed to biocides through dermal, inhalational, and oral routes. However, information on the dermal and inhalational toxicity of biocides is limited. We evaluated the effects of biocides on the skin and airways using the reconstructed human epidermis model KeraSkin™ and the airway model SoluAirway™. We determined the irritancy of 11 commonly used biocides (1,2-benzisothiazol-3(2H)-one [BIT], 2-phenoxyethanol [PE], zinc pyrithione, 2-bromo-2-nitropropane-1,3-diol, 3-iodoprop-2-ynyl N-butylcarbamate [IPBC], 2-octyl-1,2-thiazol-3-one, 2,2-dibromo-2-cyanoacetamide, 4-chloro-3-methylphenol [CC], 2-phenylphenol, deltamethrin, and 4,5-dichloro-2-octyl-1,2-thiazol-3-one) in the KeraSkin™ and SoluAirway™ by viability and histological examinations. BIT and CC were found to cause skin irritation at the approved concentrations or at the concentration close to approved limit while the others were non-irritants within the approved concentration. These results were confirmed via histology, wherein skin irritants induced erosion, vacuolation, and necrosis of the tissue. In the SoluAirway™, most of the biocides decreased cell viability even within the approved limits, except for PE, IPBC, and deltamethrin, suggesting that the airway may be more vulnerable to biocides than the skin. Taken together, our result indicates that some biocides can induce toxicity in skin and airway. Further studies on the dermal and inhalational toxicity of biocides are warranted.

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

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

Bioengineered Skin Intended as In Vitro Model for Pharmacosmetics, Skin Disease Study and Environmental Skin Impact Analysis

This review aims to be an update of Bioengineered Artificial Skin Substitutes (BASS) applications. At the first moment, they were created as an attempt to replace native skin grafts transplantation. Nowadays, these in vitro models have been increasing and widening their application areas, becoming important tools for research. This study is focus on the ability to design in vitro BASS which have been demonstrated to be appropriate to develop new products in the cosmetic and pharmacology industry. Allowing to go deeper into the skin disease research, and to analyze the effects provoked by environmental stressful agents. The importance of BASS to replace animal experimentation is also highlighted. Furthermore, the BASS validation parameters approved by the OECD (Organisation for Economic Co-operation and Development) are also analyzed. This report presents an overview of the skin models applicable to skin research along with their design methods. Finally, the potential and limitations of the currently available BASS to supply the demands for disease modeling and pharmaceutical screening are discussed.

Freezing Weakens the Barrier Function of Reconstructed Human Epidermis as Evidenced by Raman Spectroscopy and Percutaneous Permeation

The development and characterization of reconstructed human epidermis (RHE) is an active area of R&D. RHE can replace animal tissues in pharmaceutical, toxicological and cosmetic sciences, yielding scientific and ethical advantages. RHEs remain costly, however, due to consumables and time required for their culture and a short shelf-life. Storing, i.e., freezing RHE could help reduce costs but to date, little is known on the effects of freezing on the barrier function of RHE. We studied such effects using commercial EpiSkin™ RHE stored at -20, -80 and -150 °C for 1 and 10 weeks. We acquired intrinsic Raman spectra in the stratum corneum (SC) of the RHEs as well as spectra obtained following topical application of resorcinol in an aqueous solution. In parallel, we quantified the effects of freezing on the permeation kinetics of resorcinol from time-dependent permeation experiments. Principal component analyses discriminated the intrinsic SC spectra and the spectra of resorcinol-containing RHEs, in each case on the basis of the freezing conditions. Permeation of resorcinol through the frozen RHE increased 3- to 6-fold compared to fresh RHE, with the strongest effect obtained from freezing at -20 °C for 10 weeks. Due to the extensive optimization and standardization of EpiSkin™ RHE, the effects observed in our work may be expected to be more pronounced with other RHEs.

Human skin models: From healthy to disease-mimetic systems; characteristics and applications

Skin drug delivery is an emerging route in drug development, leading to an urgent need to understand the behaviour of active pharmaceutical ingredients within the skin. Given, As one of the body's first natural defences, the barrier properties of skin provide an obstacle to the successful outcome of any skin drug therapy. To elucidate the mechanisms underlying this barrier, reductionist strategies have designed several models with different levels of complexity, using non-biological and biological components. Besides the detail of information and resemblance to human skin in vivo, offered by each in vitro model, the technical and economic efforts involved must also be considered when selecting the most suitable model. This review provides an outline of the commonly used skin models, including healthy and diseased conditions, in-house developed and commercialized models, their advantages and limitations, and an overview of the new trends in skin-engineered models.

Quercetin Improves Inflammation, Oxidative Stress, and Impaired Wound Healing in Atopic Dermatitis Model of Human Keratinocytes

Background: Atopic dermatitis (AD) is a common inflammatory skin disease with complex pathogenesis. Natural flavonoids exhibit strong anti-inflammatory and antioxidant properties in many human diseases. In this study, the potential bioactive effect of quercetin, a polyphenolic plant-derived flavonoid, on the AD model of human keratinocytes was evaluated. Methods: Immortalized human HaCaT keratinocytes were treated with interleukin (IL) -4, -13, and tumor necrosis factor-α to mimic AD features in vitro. Then effects of quercetin on inflammation, oxidative stress, and wound healing were assessed. Results: Pretreatment of the cells with 1.5 μM of quercetin significantly reduced the expression of AD-induced IL-1β, IL-6, IL-8, and thymic stromal lymphopoietin, while it strongly enhanced the expression of superoxide dismutase-1 (SOD1), SOD2, catalase, glutathione peroxidase, and IL-10. Quercetin promoted wound healing by inducing epithelial-mesenchymal transition, which was supported by the upregulation of Twist and Snail mRNA expression. Unexpectedly, quercetin pretreatment of AD-induced cells upregulated the mRNA expression of occludin and E-cadherin, while downregulating matrix metalloproteinase 1 (MMP1), MMP2, and MMP9 expression. The pretreatment inhibited AD-induced phosphorylation of extracellular signal-regulated kinase 1/2/mitogen-activated protein kinase (ERK1/2 MAPK) and the expression of nuclear factor-kappa B (NF-κB), but it did not alter signal transducer and activator of transcription 6 (STAT6) phosphorylation. Conclusion: Quercetin may serve as a potential bioactive substance for atopic dermatitis-related symptoms through anti-inflammatory and antioxidant activities along with its acceleration of wound healing via ERK1/2 MAPK and NF-κB pathways.

Live imaging of alterations in cellular morphology and organelles during cornification using an epidermal equivalent model

The stratum corneum plays a crucial role in epidermal barrier function. Various changes occur in granular cells at the uppermost stratum granulosum during cornification. To understand the temporal details of this process, we visualized the cell shape and organelles of cornifying keratinocytes in a living human epidermal equivalent model. Three-dimensional time-lapse imaging with a two-photon microscope revealed that the granular cells did not simply flatten but first temporarily expanded in thickness just before flattening during cornification. Moreover, before expansion, intracellular vesicles abruptly stopped moving, and mitochondria were depolarized. When mitochondrial morphology and quantity were assessed, granular cells with fewer, mostly punctate mitochondria tended to transition to corneocytes. Several minutes after flattening, DNA leakage from the nucleus was visualized. We also observed extension of the cell-flattening time induced by the suppression of filaggrin expression. Overall, we successfully visualized the time-course of cornification, which describes temporal relationships between alterations in the transition from granular cells to corneocytes.

Restoration of calcium-induced differentiation potential and tight junction formation in HaCaT keratinocytes by functional attenuation of overexpressed high mobility group box-1 protein

HaCaT cells have been widely used as undifferentiated epidermal keratinocytes, since these non-tumorigenic cells can be readily maintained in conventional medium and partly retain epidermal differentiation potential upon stimulation with high concentration of calcium. In contrast to primary epidermal keratinocytes, however, these cells never form tight junction (TJ), a specific structure in highly differentiated keratinocytes, solely by the differentiation stimulation. Here, we show that HaCaT cells secrete a considerable amount of high mobility group box-1 protein (HMGB1), one of major inflammatory mediator, which appeared to be responsible, at least in part, for such aberrant differentiation response. So far, inhibition of c-Jun N-terminal kinase (JNK) in high calcium medium has been supposed to be the only way to induce TJ formations in HaCaT cells; however, SP600125, a potent inhibitor of JNK showed cytostatic effects and clearly attenuated epidermal differentiation and stratification. In contrast, dipotassium glycyrrhizate (GK2), a soluble analogue of HMGB1-blocker Glycyrrhizin, down-regulated interferon-β, a typical inflammatory cytokine induced by secreted HMGB1, and accelerated differentiation responses to the calcium treatment in these cells. In addition, GK2-treatmenrt resulted in the formation of double cell layers in cultured HaCaT cells, where the stratified upper cells transiently accumulated TJ proteins at the cell-cell contact sites. These results highlight the importance of attenuation of secreted HMGB1-signals in cultured HaCaT cells for studies of functional keratinocytes.

On the relevance of an in vitro reconstructed human epidermis model for drug screening in atopic dermatitis

Recent advances in the development of human-based in vitro models offer new tools for drug screening and mechanistic investigations of new therapeutic agents. However, there is a lack of evidence that disease models respond favourably to potential drug candidates. Atopic dermatitis (AD) is a very common disease associated with an altered skin barrier and chronic inflammation. Here, we demonstrate that the AD-like features of a reconstructed human epidermis (RHE) model treated with Th2 cytokines are reversed in the presence of molecules known to have a beneficial effect on damaged skin as a result of modulating various signalling cascades including the Liver X Receptors and JAK/STAT pathways. This work shows that standardized and reproducible RHE are relevant models for therapeutic research assessing new drug candidates aiming to restore epidermal integrity in an inflammatory environment.

Olive-Oil-Derived Polyphenols Effectively Attenuate Inflammatory Responses of Human Keratinocytes by Interfering with the NF-κB Pathway

SCOPE

Extra virgin olive oil (EVOO) is rich in phenolic compounds, including hydroxytyrosol (HTy) and hydroxytyrosyl acetate (HTy-Ac), which have presented multiple beneficial properties. Their impact on inflammatory responses in human keratinocytes and modes of action have not been addressed yet.

METHODS AND RESULTS

Primary human keratinocytes are pretreated with HTy-Ac or HTy for 30 min and stimulated with IL-1β or Toll-like receptor 3 ligand (TLR3-l). Thymic stromal lymphopoietin (TSLP), measured by ELISA, is attenuated by both polyphenols in a dose-dependent manner. The expression of several inflammation-related genes, including distinct TSLP isoforms and IL-8, are assessed by quantitative RT-PCR and likewise inhibited by HTy-Ac/HTy. Mechanistically, EVOO phenols counteracts IκB degradation and translocation of NF-κB to the nucleus, a transcription factor of essential significance to TSLP and IL-8 transcriptional activity; this is evidenced by immunoblotting. Accordingly, NF-κB recruitment to critical binding sites in the TSLP and IL-8 promoter is impeded in the presence of HTy-Ac/HTy, as demonstrated by chromatin immunoprecipitation. Promoter reporter assays finally reveal that the neutralizing effect on NF-κB induction has functional consequences, resulting in reduced NF-κB-directed transcription.

CONCLUSION

EVOO phenols afford protection from inflammation in human keratinocytes by interference with the NF-κB pathway.

Development of a new eczema-like reconstructed skin equivalent for testing child atopic dermatitis-relieving cosmetics

OBJECTIVE

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease, and it has serious effects on children's and families' quality of life. We aimed to screen and evaluate the efficacy of different formulas on relieving of atopic dermatitis clinical symptoms by developing an eczema-like reconstructed human skin equivalent in vitro.

METHOD

Some research has reported that thymic stromal lymphopoietin (TSLP) may be a potential therapeutic target for the treatment of AD. We developed an eczema-like in vitro skin equivalent by coculturing the cocktails polyinosinic-polycytidylic acid sodium salt (poly(I:C)) and lipopolysaccharides (LPS). The eczema-like skin equivalent was characterized by overexpression of TSLP and impaired skin barrier function. Three cosmetic formulas with the potential of anti-inflammation and skin barrier promotion were topically applied onto the eczema-like skin equivalent, mimicking in vivo application. The inhibitory effect on TSLP was examined by ELISA. Effects on tissue viability and skin barrier function were determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) method.

CONCLUSION

The results show that eczema-like skin equivalent induced by cocktails of poly(I:C) and LPS can mimic the skin characters of the atopic dermatitis. The cocktails can induce high TSLP expression, impaired cell viability, and skin barrier function. The cosmetic formulas with the potential of anti-inflammation and skin barrier promotion were evaluated to be helpful to decrease and relieve the impact of AD with the decreased TSLP and the higher tissue viability than the eczema-like skin equivalent without any cosmetic application. The eczema-like skin equivalent can be used to screen and evaluate formulas on AD relieving.

Pruritus in Autoimmune and Inflammatory Dermatoses

Pruritus in autoimmune and inflammatory dermatoses is a common symptom that can be severe and affect the quality of life of patients. In some diseases, pruritus is related to disorders activity and severity or may occur independent of the disease. Despite the high prevalence, the symptom is still underrated and there are only a few trials investigating the efficacy of drugs for disease-specific pruritus. In this review, the characteristics and possible pathomechanisms of pruritus in various dermatoses like autoimmune bullous diseases, connective tissue diseases as well as autoimmune-associated dermatoses (atopic dermatitis, psoriasis vulgaris) is illustrated. Additionally, studies analyzing the antipruritic treatment are discussed. Summarizing, the prevalence of pruritus in these diseases demonstrates the importance for symptom recognition and the need for an efficient antipruritic therapy.

Safety and efficacy of hydroxytyrosol-based formulation on skin inflammation: in vitro evaluation on reconstructed human epidermis model

BACKGROUND

Atopic dermatitis is a multifactorial immune-mediated skin disorder characterized by an alteration of epidermal barrier function and onset of skin lesions, which range from mild erythema to severe lichenification. Treatment consists in hydration with possible use of topical or immunomodulatory corticosteroids, which, however sometimes showed side effects. Recently, the interest in natural compounds has grown significantly and among these, hydroxytyrosol (HT) plays a pivotal role due to its strong and well-known anti-inflammatory activity.

OBJECTIVES

The aim of this study was to investigate the safety and efficacy of Fenolia® Eudermal Cream 15 (HT-based formulation) on epidermal barrier impaired as consequence of skin injury.

METHODS

Whit this purpose, morphologic and structural as well as anti-inflammatory evaluations, after treatment with pro-inflammatory mediators (PBS 1 X and LPS) and HT-based formulation on reconstructed human epidermis (RHE) were carried out by qualitative (hematoxylin/eosin- and immunostaining) and quantitative (MTT assay, IL-1α and IL-8 release by ELISA) techniques. Furthermore, HT absorption through the epidermal barrier was evaluated by RP-LC-DAD analysis.

RESULTS

A rise in the thickness of the epidermis as well as an appropriate maturation and protein expression (Loricrin, Fillagrin, E-Cadherin and Cytokeratins 5&6) were detected in treated RHE samples. In particular, the HT-based formulation was found to stimulate cell proliferation, as evidenced by the significant increase in Ki67 expression, which suggests the involvement of repair mechanisms, increasing epithelial regeneration and differentiation and improving the epidermal barrier effect. Furthermore, HT-based formulation showed a statistically significant anti-inflammatory activity by reducing both IL-1α and IL-8 release by RHE tissues, greater than the reference drug dexamethasone. Finally, excellent transcutaneous absorption values were found for HT, demonstrating how this new formulation increases the availability of the bioactive compound.

CONCLUSIONS

In light of these results, Fenolia® Eudermal Cream 15 could be an effective agent to counteract atopic dermatitis. Graphical abstract Safety and efficacy of hydroxytyrosol-based formulation on skin inflammation: in vitro evaluation on reconstructed human epidermis model.

Current pharmaceutical developments in atopic dermatitis

Atopic dermatitis (AD) is an inflammatory, pruritic, chronic or chronically relapsing skin disease that typically begins in early childhood and is occurring frequently in families with other atopic diseases (bronchial asthma and/or allergic rhino-conjunctivitis). Thanks to immunological and neurobiological research, the era of new treatments is coming as well as it occurred with psoriasis 15 years ago. Many treatments targeting cytokines (IL-4, IL-13, IL-31, TSLP) or neurotransmitters (substance P, opioids) or their respective receptors as well as phosphodiesterase-4 or the Jak/Stat pathways are under development. Antagonists of cytokines and anti-jak have promising effects on pruritus while it is more difficult to discriminate the effects of other drugs from the placebo effect on itch, which is known to be high.

Ameliorating effect of dipotassium glycyrrhizinate on an IL-4- and IL-13-induced atopic dermatitis-like skin-equivalent model

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is not fully understood. Defects in skin barrier function and dysregulation of the Th2 immune response are thought to be pivotal in AD pathogenesis. In this study, we used keratinocytes and AD-like skin equivalent models using Th2 cytokines IL-4 and IL-13. The keratinocytes and AD-like skin model were used to investigate the effect of dipotassium glycyrrhizinate (KG), which is widely used as an anti-inflammatory agent for AD treatment. KG decreased AD-related gene expression in keratinocytes stimulated with Th2 cytokines. KG alleviated AD-like phenotypes and gene expression patterns and inhibited release of AD-related cytokines in the AD-like skin equivalent models. These findings indicate KG has potential effectiveness in AD treatment and AD-like skin equivalent models may be useful for understanding AD pathogenesis.