Side effects of pigments used in tattoo inks on skin cells – Tattooink

One French adult out of 7 now bears at least one tattoo, a proportion peaking to almost 1 out of 4 in young adults (<35 years). Technically speaking, a tattoo represents an intradermal injection of pigments, which are resistant to degradation and therefore remain in place for the lifetime of the individual. While the acute effects of tattoos, e.g. in terms of inflammation, are now well described, their potential long-term effects remain largely unknown, and the recent evolution in terms of number of tattooed persons, tattooed body area and diversity of pigments used decrease the power of retrospective analyses. There is thus a need of biological prospective analyses to investigate potential long-term risks that may be associated with some particular features of tattoos. In this context, the TATTOOINK project will explore the potential effects of pigments used in tattoo inks on skin cells such as keratinocytes and macrophages, using a combination of proteomic and targeted approaches.
As the diversity of pigments used in tattoo inks is overwhelming, a selection of mineral, organometallic (e.g. copper phthalocyanines) and purely organic (e.g. azo pigments) will be studied.
The selected pigments will be aged in vivo in macrophages, but also in vitro through a forced ageing that will mimic the ageing taking places over several years in macrophages, i.e. the cells that sequester the pigments in situ in the dermis and thus ensure the permanency of tattoos. The effects of the pristine and aged pigments on macrophages will be studied through their phagocytic and inflammatory functions, but also through important surface markers. Upon ageing, pigments can also produce soluble or nanoparticular by-products, which can be released and impact other cell types of the skin such as keratinocytes. The impact of these by-products on keratinocytes will be studied, notably for genotoxicity, which is directly linked to carcinogenesis. These studies will use either pigments alone, or in combination with light irradiation to mimic the case of sunlight-exposed tattoos.
All in all, these data will allow a better appraisal of possible long-term effects of pigments used in tattoo inks. The proposed method, which uses in vitro approaches, follows the 3R rules (Reduce Refine, Replace), which aim at limiting the use of laboratory animals. This method can be used then for other pigments, or other persistent metallic or nanoparticular contaminants.