Immortalized keratinocytes cells generates an effective model of Epidermal Human Equivalent for irritation and corrosion tests

Reliability and relevance of the ES®-RHE model for in vitro skin irritation test application

INTRODUCTION

In vitro methods have been widely used to assess adverse effects. Reconstructed Human Epidermis (RHE) poses as a fascinating test system employed to assess the dermal irritation hazard potential of chemicals. Although several RHE models are reported in the OECD Test Guideline No. 439, the OECD Document No. 220 encourages the scientific community to develop and validate new RHE test systems due to its relevance for socio-economic advancement.

METHODS

Following the criteria documented in the OECD No. 220, a blind study for skin irritation (OECD 439) was conducted employing the Minimum List of Reference Chemicals for Determination of Reproducibility and Predictive Capacity using ES®-RHE. Structural and functional characteristics were assessed alongside the prediction model.

RESULTS

The model has shown reproducibility of optical density and barrier function, similarly to internationally validated methods. Furthermore, it shows the cell layers' development and differentiation ability due to Cytokeratin14, Cytokeratin10, and filaggrin expression. The prediction model resulted in sensitivity, specificity and accuracy rates of 100, 70, and 77 %, respectively.

CONCLUSIONS

The ES®-RHE demonstrated reliability and relevance, with similar structural and functional characteristics comparable to internationally validated models, in addition to the accepted predictive capacity according to OECD required minimum criteria, thus confirming the suitability of the national ES®-RHE in the hazard prediction of dermal irritation based on OECD Test Guideline No. 439.

Research progress in the development of 3D skin models and their application to in vitro skin irritation testing

Toxicological assessment of chemicals is crucial for safeguarding human health and the environment. However, traditional animal experiments are associated with ethical, technical, and predictive limitations in assessing the toxicity of chemicals to the skin. With the recent development of bioengineering and tissue engineering, three-dimensional (3D) skin models have been commonly used as an alternative for toxicological studies. The skin consists of the subcutaneous, dermis, and epidermis. All these layers have crucial functions such as physical and biological protection and thermoregulation. The epidermis is the shallowest layer protecting against external substances and media. Because the skin is the first contact point for many substances, this organ is very significant for assessing local toxicity following skin exposure. According to the classification of the United Nations Global Harmonized System, skin irritation is a major potentially hazardous characteristic of chemicals, and this characteristic must be accurately assessed and classified for enhancing chemical safety management and preventing and reducing chemical accidents. This review discusses the research progress of 3D skin models and introduces their application in assessing chemical skin irritation.

Ergothioneine-Sodium Hyaluronate Dressing: A Promising Approach for Protecting against Radiation-Induced Skin Injury

Radiotherapy commonly causes damage to healthy tissues, particularly radiation-induced skin injury (RISI) that affects a significant majority of patients undergoing radiotherapy. Effective treatments for RISI are lacking. This study focuses on the pathogenesis of RISI, which primarily involves oxidative stress. Excessive reactive oxygen species (ROS) generation during radiation induces damage to biological macromolecules, triggering oxidative stress and inflammation. To address this, ergothioneine (EGT), a natural and biocompatibile thiol compound with excellent antioxidant activity, is explored as a potential radiation-protective agent. By utilizing its specific transport and absorption in the skin tissue, as well as its efficient and stable clearance of radiation-induced "ROS storm", EGT is combined with sodium hyaluronate (NaHA) to develop a novel radiation protective dressing suitable for the skin. This EGT-NaHA dressing demonstrates an effective ability to scavenge free radicals and reduce oxidative stress in vitro and in vivo, reducing cellular apoptosis and inflammation. These results demonstrate the protective properties of EGT against RISI, with far-reaching implications for research and development in the field of radioprotection.

Depigmenting effect of Xanthohumol from hop extract in MNT-1 human melanoma cells and normal human melanocytes

Xanthohumol (XH) is the most abundant prenylated flavonoid found in the hop plant (Humulus lupulus L.) and has previously been shown to have depigmenting effects in B16F10 mouse melanoma cells; however, studies of its depigmenting efficacy in human melanocytes are still lacking. In this work, we explored the effects of XH on melanogenesis in MNT-1 human melanoma cells and normal human melanocytes from darkly-pigmented skin (HEM-DP). XH was screened for cytotoxicity over 48 h, and subsequently tested on melanogenesis in MNT-1 cells. XH was further tested in HEM-DP cells for melanin synthesis and melanosome export; dendricity was quantitated to assess effects on melanosome export. Melanosome degradation was studied in human keratinocytes (HaCaT). Our results showed that XH inhibited melanin synthesis in MNT-1 cells at 30 μM but increased intracellular tyrosinase activity without affecting ROS levels. In HEM-DP cells, XH robustly suppressed cellular tyrosinase activity at nontoxic concentrations (2.5–5 μM) without any effect on melanin synthesis. However, XH inhibited melanosome export by reducing dendrite number and total dendrite length. Further testing in HaCaT cells demonstrated that XH induced melanosome degradation at low micromolar concentrations without any cytotoxicity. In summary, our results demonstrate that XH at low micromolar concentrations might hold promise as a potent inhibitor of human pigmentation by primarily targeting melanin export and melanin degradation. Further studies to elucidate the signaling mechanisms of action of melanosome export inhibition by XH and in vivo efficacy are warranted.

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Xanthohumol (XH) inhibited melanin synthesis in MNT-1 human melanoma cells.

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XH did not inhibit melanin synthesis in primary human melanocytes but significantly suppressed both dendrite number and total dendrite length at low micromolar concentrations.

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Reduction of melanosome export by reduction in dendricity was correlated with the inhibition of intracellular tyrosinase activity.

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XH induced melanosome degradation in human keratinocytes.

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XH is a candidate for skin-lightning which inhibits human melanogenesis by targeting later steps in melanogenesis.