The development of alternative approaches for safety and efficacy testing that avoid the use of animals is a worldwide trend, which relies on the improvement of current models and tools so that they better reproduce human biology. Human skin from elective plastic surgery is a promising experimental model to test the effects of topically applied products. As the structure of native skin is maintained, including cell population (keratinocytes, melanocytes, Langerhans cells and fibroblasts) and dermal matrix (containing collagen, elastin, glycosaminoglycans, etc.), it most closely matches the effects of substances on in vivo human skin. In this review, we present a collection of results that our group has generated over the last years, involving the use of human skin and scalp explants, demonstrating the feasibility of this model. The development of a test system with ex vivo skin explants, of standard size and thickness, and cultured at the air–liquid interface, can provide an important tool for understanding the mechanisms involved in several cutaneous disorders.

BACKGROUND Pollution, especially cigarette smoke, is a major cause of skin damage. OBJECTIVES To assess the effects of the small molecule polyphenol, honokiol, on reversing cigarette smoke induced damage in vitro to relevant skin cells. METHODS Keratinocytes (HaCat) cultures were exposed to cigarette smoke and, after 48 hours, IL-1α and IL-8 were measured in cell supernatants. Moreover, TIMP-2 production, apoptosis rate, and senescence β-galactosidase expression were evaluated in primary human fibroblasts (HFF-1) cultures. RESULTS Honokiol at 10 μM reduced IL-1α production by 3.4 folds (p<0.05), and at 10 and 20 μM reduced IL-8 by 23.9% and 53.1% (p<0.001), respectively, in HaCat keratinocytes. In HFF-1, honokiol restored TIMP-2 production by 96.9% and 91.9% (p<0.001), respectively, at 10 and 20 μM, as well as reduced apoptosis by 47.1% (p<0.001) and 41.3% (p<0.01), respectively. Finally, honokiol reduced senescence associated β-galactosidase expression in HFF-1. CONCLUSION Honokiol protects both HFF-1 and HaCat against cigarette smoke induced inflammation, collagenolysis, apoptosis, and senescence.

Sebaceous glands (SG) are localized almost on the entire surface of skin and present as primary function, the production and secretion of sebum. Sebum consists of a mixture of triglycerides, free fatty acids, cholesterol, and esters that perform protective functions in waterproofing, lubrication, protection against friction, transport of antioxidants, among others. 1-3 Sebaceous glands activity can be upregulated by many factors, particularly androgens. Dihydrotestosterone (DHT) is the androgen with the highest biological activity in tissue, being converted intracellularly from testosterone by the action of the 5α-reductase

Background: Melanin plays an important role in protecting the skin against the harmful effects of solar radiation, but its abnormal accumulation may become an aesthetic problem, such as melasma and age spots. Aims: The aim of this study was to evaluate the antiangiogenic and whitening effects of a depigmentation formulation (BLTX) using an in vitro model of human cell and skin culture. Methods: Human fibroblasts, keratinocytes or melanocytes were treated with BLTX and subjected to oxidative stress by UV radiation or inflammatory stress with IL-1α for quantification of melanin, tyrosinase, endothelin-1, PAR-2, VEGF and iNOS. Fragments of human skin, from elective plastic surgery, were treated with BLTX and subjected to histological evaluation with hematoxylin/eosin associated with Fontana-Masson technique for melanin view. A parametric method, the one-way analysis of variance (ANOVA) followed by the Bonferroni test, was used to compare data among all groups. Results: The results demonstrated that BLTX promotes a reduction in VEGF and iNOS protein synthesis in cultured dermal fibroblasts, indicating an antiangiogenic property. In relation to whitening effect, BLTX was able to reduce the production of melanin in both systems, melanocytes and human skin cultures. The depigmenting action was also revealed by decreasing the levels of endothelin-1, PAR-2 and activity of tyrosinase, when compared to cultures exposed to UV radiation. Conclusion: The results allow us to infer that BLTX presents an antiangiogenic effect indicating a role in the vascular component of melasma. Furthermore, the whitening property observed reinforces its use in the prevention and treatment of melasma.

Native human skin has been reported in the literature as being an important experimental model for studying skin biology. Studies performed by our group have shown that ex vivo skin, from elective plastic surgery, maintains the biological characteristics of native skin under specific culture conditions. As such, it might be a feasible model for the safety and efficacy testing of topical substances. While Brazil is at the forefront of global regulation implementation, Brazilian researchers are not always able to transfer certain widely used protocols to their laboratories, particularly protocols that involve the use of reconstructed tissues with limited viability, such as those for skin corrosion (OECD TG 431) and irritation testing (OECD TG 439). In this study, we investigated the applicability of the ex vivo skin model to the evaluation of irritation and corrosion potential of a number of proficiency substances described in TG 431 and TG 439. The skin fragments were standardised in size and diameter, and placed into cell culture inserts. The experimental protocol was conducted according to TG 431 and TG 439. The results obtained show that ex vivo skin could represent a promising tool for the evaluation of irritation and corrosion potential of substances (subject to inclusion and exclusion criteria), as recommended by OECD guidelines. While this is a proof-of-concept study, the use of ex vivo skin should be considered for such testing.