Application of an in vitro reconstructed human skin on cosmetics in skin irritation tests

In vitro 3D skin culture and its sustainability in toxicology: a narrative review

In current toxicological research, 2D cell cultures and animal models are well- accepted and commonly employed methods. However, these approaches have many drawbacks and are distant from the actual environment in human. To embrace this, great efforts have been made to provide alternative methods for non-animal skin models in toxicology studies with the need for more mechanistically informative methods. This review focuses on the current state of knowledge regarding the in vitro 3D skin model methods, with different functional states that correspond to the sustainability in the field of toxicology testing. We discuss existing toxicology testing methods using in vitro 3D skin models which provide a better understanding of the testing requirements that are needed. The challenges and future landscape in using the in vitro 3D skin models in toxicology testing are also discussed. We are confident that the in vitro 3D skin models application may become an important tool in toxicology in the context of risk assessment.

Magnolia biondii flower extract attenuates UVB-induced skin damage through high-mobility group box protein B1

OBJECTIVE

Magnolia biondii, a plant containing many magnolian-like compounds in its flowers or buds, exhibits anti-inflammatory and antiallergic effects; however, no study has addressed its effect on alleviating ultraviolet light (UV)-induced skin damage. We thus aimed at studying the effects of M. biondii flower extract (MB) on UVB-induced skin damage and determine the relationship between cell damage and damage-associated molecular patterns (DAMPs).

METHODS

Reconstructed epidermal models and foreskin samples were selected to detect cellular reactions after UVB irradiation and MB treatment. MTT, haematoxylin-eosin and immunofluorescence staining were used to examine total viability, sunburned cells and expression and migration of DAMPs at 16 or 48 h. Prostaglandin E2 (PGE-2) and interleukin 8 (IL-8) levels were measured using enzyme-linked immunosorbent assays. A clinical UVB-damaged test was carried out on human arms subjected to MB pre- or post-treatment. Human skin probes were used to measure erythema, melanin, ITA° and transepidermal water loss (TEWL), while skin photos were captured using the VISIA system.

RESULTS

MB is rich in lignans such as magnolin, pinoresinol dimethyl ether and fargesin, and shows weak UV absorption at 280-320 nm. Coculturing with MB for 16 or 48 h after UVB irradiation improved the tissue viability and structure of Skinovo-Epi, and reduced the expression and migration of high mobility group box protein B1 (HMGB1) as well as the expression of IL-8 and PGE-2. In the excised foreskin treated with MB after UVB irradiation, the generation of 8-hidroxy-2-deoxyguanosine and nuclear transfer of HMGB1 were reduced. When pre-treated with MB for 3 days, UVB-induced skin erythema and ITA° were significantly decreased. When post-treated with MB for 5 days, a decrease in skin erythema, melanin and TEWL values and an increase in skin ITA° were observed.

CONCLUSIONS

Treatment with MB attenuated UVB-induced skin damage, such as erythema, pigmentation and skin barrier function, by improving the tissue viability and structure and reducing sunburned cells and skin inflammation. This effect may be related to DNA damage, which causes the migration of HMGB1 from the nucleus to the outside of the cell to induce skin inflammation.

Prinsepia utilis Royle polysaccharides promote skin barrier repair through the Claudin family

BACKGROUND

Plant polysaccharides have various biological activities. However, few studies have been conducted on the skin barrier of Prinsepia utilis Royle polysaccharide extract (PURP).

MATERIALS AND METHODS

The proportions of polysaccharides, monosaccharides and proteins were determined by extracting polysaccharides from fruit meal using water. The healing rate was measured by cell scratch assays. SDS-damaged reconstructed human epidermal models, an acetone-ether-induced mouse model and an IL-4-induced cellular inflammation model were used to detect the effects of polysaccharides on the phenotype, HA, TEWL, and TEER, with further characterizations performed using QRT-PCR, Western blotting, immunofluorescence (IF) assays.

RESULTS

PURP contained 35.73% polysaccharides and 11.1% proteins. PURP promoted cell migration and increased skin thickness in a reconstructed human epidermis model. The TEWL significantly decreased, and the HA content significantly increased. PURP significantly increased the TEER and decreased the permeability of the SDS-damaged reconstructed human epidermis model. Claudin-3, Claudin-4, and Claudin-5 were significantly upregulated. IF and Western blot analysis revealed that the Claudin-4 level significantly increased after treatment with PURP. Claudin-1, Claudin-3, Claudin-4, and Claudin-5 gene expression and IF and immunohistochemical staining were significantly increased in mice treated with acetone-ether. PURP promoted the expression of Claudin-1, Claudin-3, Claudin-4, and Claudin-5 after treatment with 100 ng/mL IL-4. PURP also downregulated the expression of NO, IL6, TNFα and NFκB in Raw 264.7 cells and in a mouse model.

CONCLUSION

We hypothesize that PURP may repair the skin barrier by promoting the expression of the claudin family and can assist in skin therapy.

Skin Rejuvenation Efficacy and Safety Evaluation of Kaempferia parviflora Standardized Extract (BG100) in Human 3D Skin Models and Clinical Trial

Polymethoxyflavones from Kaempferia parviflora rhizomes have been shown to effectively combat aging in skin cells and tissues by inhibiting senescence, reducing oxidative stress, and enhancing skin structure and function. This study assessed the anti-aging effects and safety of standardized K. parviflora extract (BG100), enriched with polymethoxyflavones including 5,7-dimethoxyflavone, 5,7,4'-trimethoxyflavone, 3,5,7,3',4'-pentamethoxyflavone, 3,5,7-trimethoxyflavone, and 3,5,7,4'-tetramethoxyflavone. We evaluated BG100's impact on skin rejuvenation and antioxidant properties using photoaged human 3D full-thickness skin models. The potential for skin irritation and sensitization was also assessed through studies on reconstructed human epidermis and clinical trials. Additionally, in vitro genotoxicity testing was performed following OECD guidelines. Results indicate that BG100 promotes collagen and hyaluronic acid production, reduces oxidative stress, and minimizes DNA damage in photoaged full-thickness 3D skin models. Furthermore, it exhibited non-irritating and non-sensitizing properties, as supported by tests on reconstructed human epidermis and clinical settings. BG100 also passed in vitro genotoxicity tests, adhering to OECD guidelines. These results underscore BG100's potential as a highly effective and safe, natural anti-aging agent, suitable for inclusion in cosmeceutical and nutraceutical products aimed at promoting skin rejuvenation.

Preparation and characterization of astaxanthin-loaded biodegradable polyhydroxybutyrate (PHB) microbeads for personal care and cosmetic applications

Due to its biodegradability and biocompatibility, polyhydroxybutyrate (PHB) has received attention as an alternative material for microbeads in personal care and cosmetic products (PCCPs). Here, PHB was produced from crude glycerol by an Escherichia coli JM109 strain harboring pUC19-23,119-phaCABA-04 without isopropyl β-D-1-thiogalactopyranoside (IPTG), an inducing agent. Astaxanthin-loaded PHB microbeads were prepared through emulsification-solvent evaporation. Studies were performed to determine how the concentration of PHB and stirring rate influence the size, surface morphology, encapsulation efficiency (EE), and astaxanthin release profile. The astaxanthin-loaded PHB microbeads exhibited a rough surface, 98.1 ± 0.7 % EE, spherical shape and 179 ± 44 μm size. In addition, <50 % astaxanthin release was observed within 240 min. Stability studies revealed that astaxanthin-loaded microbeads retained over 85.3 ± 4.2 % of astaxanthin after 90 days at 4 °C and showed a 2-fold reduction in astaxanthin degradation compared to their unencapsulated counterparts; thus, astaxanthin-loaded microbeads show promise for PCCPs applications. A cytotoxicity assay revealed that astaxanthin-loaded PHB microbeads were nontoxic to the human epidermal keratinocyte cell line, PSVK1, and EpiSkin® cells. Skin irritation and sensitization were not observed during a human repeated insult patch test (HRIPT), according to clinical practice guidelines of the Japanese dermatological association.

Glycolipid Biosurfactants in Skincare Applications: Challenges and Recommendations for Future Exploitation

The 21st century has seen a substantial increase in the industrial applications of glycolipid biosurfactant technology. The market value of the glycolipid class of molecules, sophorolipids, was estimated to be USD 409.84 million in 2021, with that of rhamnolipid molecules projected to reach USD 2.7 billion by 2026. In the skincare industry, sophorolipid and rhamnolipid biosurfactants have demonstrated the potential to offer a natural, sustainable, and skin-compatible alternative to synthetically derived surfactant compounds. However, there are still many barriers to the wide-scale market adoption of glycolipid technology. These barriers include low product yield (particularly for rhamnolipids) and potential pathogenicity of some native glycolipid-producing microorganisms. Additionally, the use of impure preparations and/or poorly characterised congeners as well as low-throughput methodologies in the safety and bioactivity assessment of sophorolipids and rhamnolipids challenges their increased utilisation in both academic research and skincare applications. This review considers the current trend towards the utilisation of sophorolipid and rhamnolipid biosurfactants as substitutes to synthetically derived surfactant molecules in skincare applications, the challenges associated with their application, and relevant solutions proposed by the biotechnology industry. In addition, we recommend experimental techniques/methodologies, which, if employed, could contribute significantly to increasing the acceptance of glycolipid biosurfactants for use in skincare applications while maintaining consistency in biosurfactant research outputs.

Influence of the emulsifier on nanostructure and clinical application of liquid crystalline emulsions

Liquid crystals are appealing in pharmaceutical and cosmetic fields due to their unique structures that combine the properties of both liquid and solid states. Forming an emulsion into liquid crystals can be affected by a number of factors, including the emulsion composition and temperature. Changing the types and concentrations of surfactants could be another factor that affects liquid crystals. Currently, most liquid crystal research focuses on the nanostructure of liquid crystal systems without evaluating the efficacy of liquid crystals clinically. In this study, liquid crystalline emulsions made from camellia seed oil with four different surfactants (Olivem 1000, Polyaquol-2W, Nikkomulese LC, and Lecinol S-10 with Tween 80) were created. The liquid crystal emulsions were formulated in the form of oil-in-water (o/w) emulsions with Camellia oleifera seed oil serving as the main ingredient in the oil phase (10% w/w). All formulations exhibited liquid crystal characteristics with lamellar structures as determined by the polarized light microscopy and small-angle X-ray scattering with supporting data of the nanostructure from wide-angle X-ray scattering and differential scanning calorimetry (DSC). They all showed good stability under normal (room temperature) and accelerated conditions (4 °C and 40 °C) in long-term storage (6 months). Using the reconstructed human epidermis as a skin model, all formulations did not cause skin irritation. In the clinical trial, all formulations were able to reduce transepidermal water loss (TEWL) and increase skin hydration immediately after application. This lasted at least 10 h. All formulations showed distinct Maltese crosses under the polarized light microscope with a positive result for liquid crystals in wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) methods. Moreover, among all formulations tested, Formulation D, which contained Lecinol S-10 and Tween 80 as emulsifiers, showed the most robust interaction between the surfactant and water molecules in the lamellar structure under DSC. The formulation was stable in long-term normal and accelerated conditions. Above all, Formulation D, which was formulated with Lecinol S-10 with Tween 80, had the best clinical result, was nonirritating to the skin, and can be used as a cream base in the pharmaceutical and cosmeceutical sectors.

Design, Formulation, and Evaluation of Aloe vera Gel-Based Capsaicin Transemulgel for Osteoarthritis

Topical treatments are a potential therapeutic option for the therapy of osteoarthritis, with significant data supporting the effectiveness and safety of topical formulation. Topical gel formulations may offer an alternative to oral formulations to relieve osteoarthritis (OA) pain while decreasing systemic exposure. Topical capsaicin transemulgel may represent an effective and safe alternative. The transemulgel was prepared from aqueous Aloe vera gel and Carbopol 934 with capsaicin in clove oil emulsion. The optimized transemulgel of capsaicin showed a pH of 6.1 ± 0.1 and viscosity of 15263–998 cps. Data from in vitro diffusion demonstrated improved permeability properties. The formulation caused no skin irritation when applied topically. The optimal transemulgel spreadability was found to be 20.23 g·cm/s. In vitro and ex vivo studies of the optimized formulation were performed. The skin irritant test was performed on rat skin with an optimized and marketed formulation. Both showed no irritation on the skin. The transemulgel of the capsaicin with Aloe vera gel was proven to be effective for osteoarthritis therapy.

3D Cell Cultures: Evolution of an Ancient Tool for New Applications

Recently, research is undergoing a drastic change in the application of the animal model as a unique investigation strategy, considering an alternative approach for the development of science for the future. Although conventional monolayer cell cultures represent an established and widely used in vitro method, the lack of tissue architecture and the complexity of such a model fails to inform true biological processes in vivo. Recent advances in cell culture techniques have revolutionized in vitro culture tools for biomedical research by creating powerful three-dimensional (3D) models to recapitulate cell heterogeneity, structure and functions of primary tissues. These models also bridge the gap between traditional two-dimensional (2D) single-layer cultures and animal models. 3D culture systems allow researchers to recreate human organs and diseases in one dish and thus holds great promise for many applications such as regenerative medicine, drug discovery, precision medicine, and cancer research, and gene expression studies. Bioengineering has made an important contribution in the context of 3D systems using scaffolds that help mimic the microenvironments in which cells naturally reside, supporting the mechanical, physical and biochemical requirements for cellular growth and function. We therefore speak of models based on organoids, bioreactors, organ-on-a-chip up to bioprinting and each of these systems provides its own advantages and applications. All of these techniques prove to be excellent candidates for the development of alternative methods for animal testing, as well as revolutionizing cell culture technology. 3D systems will therefore be able to provide new ideas for the study of cellular interactions both in basic and more specialized research, in compliance with the 3R principle. In this review, we provide a comparison of 2D cell culture with 3D cell culture, provide details of some of the different 3D culture techniques currently available by discussing their strengths as well as their potential applications.

Application of in vitro methods to evaluate the safety of baby care products

Draize rabbit eye irritation and skin irritation tests are widely used in the chemical industry as traditional methods to evaluate the safety of cosmetics. However, great differences among laboratories have caused great doubt in the industry. In addition, with vigorous development of the global animal protection movement, developed countries have launched the "3R" campaign, and various kinds of in vitro alternative methods have emerged. Hen's egg test on the chorioallantoic membrane (HET-CAM), which is similar to the structure of the human cornea and has a clear and complete vascular system, is based on the characteristics of the chorioallantoic membrane (CAM) in mid-term SPF egg embryos. The reconstructed human epidermis (EpiSkin®) is composed of normal human keratinocytes that are histologically similar to human epidermises seen in vivo, and it is cultured on a collagen matrix. Similar to EpiSkin®, Human Corneal Epithelium (SkinEthic™) is another reconstructed 3D human-corneal structure that is an alternative to the traditional eye irritation test. Three in vitro methods were conducted to evaluate the safety of 12 baby care products, which included the most common types. In addition, a consumer research study was also carried out for two weeks to evaluate the safety. The results of the reconstructed human epidermis model, human corneal epithelium model and consumer research showed that no irritation was found in any test products; however, HET-CAM tests showed positive results.