TatS: a novel in vitro tattooed human skin model for improved pigment toxicology research

No effect of tattoos on local sweat concentrations of select cytokines, cortisol, glucose, blood urea nitrogen, or lactate during exercise

Due to growing interest in the investigation of exercise induced sweat biomarkers to assess an individual's health and the increasing prevalence of tattoos in the world's population, investigators sought to determine whether local sweat concentrations and excretion rates of epidermal growth factor (EGF), interleukin (IL) -1α, IL-6, IL-8, cortisol, glucose, blood urea nitrogen (BUN), and lactate differ between tattooed and contralateral non-tattooed skin during exercise. Sixteen recreational exercisers [female (50%)] (age = 25-48 years) with ≥ 1 unilateral permanent tattoo [median tattoo age = 6 years, IQR = 5] on the arm/torso completed an outdoor group fitness session. There were no significant differences between tattooed and non-tattooed skin for sweat EGF, IL-1α, IL-8, cortisol, glucose, BUN, or lactate concentrations. There were no significant differences between tattooed and non-tattooed skin for sweat EGF, IL-1α, IL-8, cortisol, glucose, BUN, or lactate excretion rate. Findings suggest that permanent tattoos older than 1 year may not impact local sweat EGF, IL-1α, IL-8, cortisol, glucose, BUN, and lactate concentrations or excretion rates during exercise.Clinical trial identifier NCT04920266 was registered on June 9, 2021.

Lessons learned in a decade: Medical-toxicological view of tattooing

Tattooing has been part of the human culture for thousands of years, yet only in the past decades has it entered the mainstream of the society. With the rise in popularity, tattoos also gained attention among researchers, with the aim to better understand the health risks posed by their application. 'A medical-toxicological view of tattooing'-a work published in The Lancet almost a decade ago, resulted from the international collaboration of various experts in the field. Since then, much understanding has been achieved regarding adverse effects, treatment of complications, as well as their regulation for improving public health. Yet major knowledge gaps remain. This review article results from the Second International Conference on Tattoo Safety hosted by the German Federal Institute for Risk Assessment (BfR) and provides a glimpse from the medical-toxicological perspective, regulatory strategies and advances in the analysis of tattoo inks.

Layer-by-Layer Analysis of In Vitro Skin Models

In vitro human skin models are evolving into versatile platforms for the study of skin biology and disorders. These models have many potential applications in the fields of drug testing and safety assessment, as well as cosmetic and new treatment development. The development of in vitro skin models that accurately mimic native human skin can reduce reliance on animal models and also allow for more precise, clinically relevant testing. Recent advances in biofabrication techniques and biomaterials have led to the creation of increasingly complex, multilayered skin models that incorporate important functional components of skin, such as the skin barrier, mechanical properties, pigmentation, vasculature, hair follicles, glands, and subcutaneous layer. This improved ability to recapitulate the functional aspects of native skin enhances the ability to model the behavior and response of native human skin, as the complex interplay of cell-to-cell and cell-to-material interactions are incorporated. In this review, we summarize the recent developments in in vitro skin models, with a focus on their applications, limitations, and future directions.

Phototoxic or Photoprotective?-Advances and Limitations of Titanium (IV) Oxide in Dermal Formulations-A Review

The widespread role of titanium (IV) oxide (TiO₂) in many industries makes this substance of broad scientific interest. TiO₂ can act as both a photoprotector and photocatalyst, and the potential for its role in both applications increases when present in nanometer-sized crystals. Its sunlight-scattering properties are used extensively in sunscreens. Furthermore, attempts have been made to incorporate TiO₂ into dermal formulations of photolabile drugs. However, the propensity to generate reactive oxygen species (ROS) rendering this material potentially cytotoxic limits its role. Therefore, modifications of TiO₂ nanoparticles (e.g., its polymorphic form, size, shape, and surface modifications) are used in an effort to reduce its photocatalytic effects. This review provides an overview of the potential risks arising from and opportunities presented by the use of TiO₂ in skin care formulations.

Tattoo inks are toxicological risks to human health: A systematic review of its ingredients, fate inside skin, toxicity due to polycyclic aromatic hydrocarbons, primary aromatic amines, metals, and overview of regulatory frameworks

Today, tattooing has become very popular among people all over the world. Tattooists, with the help of tiny needles, place tattoo ink inside the skin surface and unintentionally introduce a large number of unknown ingredients. These ingredients include polycyclic aromatic hydrocarbons (PAHs), heavy metals, and primary aromatic amines (PAAs), which are either unintentionally introduced along with the ink or produced inside the skin by different types of processes for example cleavage, metabolism and photodecomposition. These could pose toxicological risks to human health, if present beyond permissible limits. PAH such as Benzo(a)pyrene is present in carbon black ink. PAAs could be formed inside the skin as a result of reductive cleavage of organic azo dyes. They are reported to be highly carcinogenic by environmental protection agencies. Heavy metals, namely, cadmium, lead, mercury, antimony, beryllium, and arsenic are responsible for cancer, neurodegenerative diseases, cardiovascular, gastrointestinal, lungs, kidneys, liver, endocrine, and bone diseases. Mercury, cobalt sulphate, other soluble cobalt salts, and carbon black are in Group 2B, which means they may cause cancer in humans. Cadmium and compounds of cadmium, on the other hand, are in Group 1 (carcinogenic to humans). The present article addresses the various ingredients of tattoo inks, their metabolic fate inside human skin and unintentionally added impurities that could pose toxicological risk to human health. Public awareness and regulations that are warranted to be implemented globally for improving the safety of tattooing.

Cutaneous Malignancies in Tattoos, a Case Series of Six Patients

Background: A variety of side effects following the tattooing of the skin were reported over the years. Analytical studies showed that some tattoo inks contain harmful compounds. Methods: We presented six patient cases with cutaneous malignancies in tattooed skin and performed an extensive literature research. Results: Two patients with black ink tattoos that were diagnosed with malignant melanoma raises the number of described cases to 36 patients. One of the patients developed an immunologic reaction limited to the tattoo area after treatment with a targeted immune therapy. In the other patient, the malignancy (malignant melanoma) was fatal. Basal cell carcinoma was seen in four patients with tattoos containing varying ink colors (black, green, red). This increased the number of described patient cases to 18. Although some ink components and their cleavage products have carcinogenic properties, epidemiological evidence for a causative correlation fails. Further epidemiologic studies on tattoos and malignancies, as well as on the appearance of naevi in tattoos, are necessary. Determining the type of mutation might be helpful to separate sun-induced tumors from skin cancers due to other pathogenic mechanisms.

Commensal-Related Changes in the Epidermal Barrier Function Lead to Alterations in the Benzo[a]Pyrene Metabolite Profile and Its Distribution in 3D Skin

Polycyclic aromatic hydrocarbons (PAH) such as benzo[a]pyrene (B[a]P) are among the most abundant environmental pollutants, resulting in continuous exposure of human skin and its microbiota. However, effects of the latter on B[a]P toxicity, absorption, metabolism, and distribution in humans remain unclear. Here, we demonstrate that the skin microbiota does metabolize B[a]P on and in human skin in situ, using a recently developed commensal skin model. In this model, microbial metabolism leads to high concentrations of known microbial B[a]P metabolites on the surface as well as in the epidermal layers. In contrast to what was observed for uncolonized skin, B[a]P and its metabolites were subject to altered rates of skin penetration and diffusion, resulting in up to 58% reduction of metabolites recovered from basal culture medium. The results indicate the reason for this altered behavior to be a microbially induced strengthening of the epidermal barrier. Concomitantly, colonized models showed decreased formation and penetration of the ultimate carcinogen B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE), leading, in consequence, to fewer BPDE-DNA adducts being formed. Befittingly, transcript and expression levels of key proteins for repairing environmentally induced DNA damage such as xeroderma pigmentosum complementation group C (XPC) were also found to be reduced in the commensal models, as was expression of B[a]P-associated cytochrome P450-dependent monooxygenases (CYPs). The results show that the microbiome can have significant effects on the toxicology of external chemical impacts. The respective effects rely on a complex interplay between microbial and host metabolism and microbe-host interactions, all of which cannot be adequately assessed using single-system studies.

Phototoxic versus photoprotective effects of tattoo pigments in reconstructed human skin models: In vitro phototoxicity testing of tattoo pigments: 3D versus 2D

The increasing number of tattooed persons urges the development of reliable test systems to assess tattoo associated risks. The alarming prevalence of 60 % phototoxic reactions in tattoos ask for a more comprehensive investigation of phototoxic reactions in tattooed skin. Here, we aimed to compare the cellular responses of human skin cells to ultraviolet (UV)A and UVB irradiation in doses of short to intermitted sun exposure (3-48 J/cm² and 0.05-5 J/cm², respectively) in the presence of tattoo pigments. Therefore, we used fibroblast monolayer culture (2D), our recently developed three dimensional full-thickness skin model with dermal-located tattoo pigments (TatS_FT) and its dermal equivalents (TatS_DE) that lack keratinocytes. We tested the most frequently used tattoo pigments carbon black, titanium dioxide (TiO₂) anatase and rutile as well as Pigment Orange (P.O.)13 in ranges from 0.067 to 2.7 ng/cell in 2D. For TatS_DE and TatS_FT, concentrations were 1.3 ng/cell for TiO₂, 0.67 ng/cell for P.O.13 and 0.067 ng/cell for carbon black. We assessed cell viability and cytokine release in all systems, and cyclobutane pyrimidine dimer (CPD) formation in TatS_FT. Phototoxicity of tattoo pigments was exclusively observed in 2D, where especially TiO₂ anatase induced phototoxic effects in all concentrations (0.067-2.7 ng/cell). In contrast, fibroblasts were protected from UV irradiation in TatS_DE by TiO₂ and carbon black. Neither toxic nor protective effects were recorded in TatS_FT. P.O.13 showed altered cytokine secretion in 2D (0.067-1.3 ng/cell) and TatS_DE, despite the absence of significant effects on viability in all systems. All pigments reduced the number of CPDs in TatS_FT compared to the pigment-free controls. In conclusion, our study shows that within a 3D arrangement, intradermal tattoo pigments may act photoprotective despite intrinsic phototoxic properties in 2D. Thus, dermal 3D equivalents should be considered to evaluate acute tattoo pigment toxicology.