Why do tattoos last so long?
Tattoos are a very old and, these days, pretty common. Even for science, it is a trendy topic and today we will talk about why tattoos last so long and why it is difficult to eliminate them.
Tattooing involves injecting water-insoluble pigments into the skin. To be more precise, into the dermis. When you get a tattoo, the skin is damaged and the pigments can penetrate it. This damage alerts the immune system, which "cleans" the affected area. It has been observed that quickly after tattooing, a fraction of these pigments is removed. The pigments that remain at the site of the injection –at the end of the day, those that maintain the tattoo color–, are "captured" and internalized by a specific type of immune cells: dermal macrophages. Previously, it was thought that the cells that captured the pigments had very long-lasting life, which explained the permanence of the tattoo. However, the researchers observed that the dermal macrophages underwent a continuous renewal (at least in mice). Therefore, they proposed a new model of capture, release and re-capture. That is, when a dermal macrophage dies, releases the pigments and other neighboring macrophages re-captures them, thus maintaining the "stability" of the tattoo for years.
Understanding these processes, goes beyond the simple curiosity of the scientists. For example, nowadays to eliminate tattoos several sessions with laser are required to destroy the cells that carry the pigments. Despite this procedure, some tattoos do not disappear because a percentage of the released pigments are recaptured by neighboring cells, maintaining skin staining. But now, we understand these procedures and we can think on more effective treatments to eliminate them, such as mixing laser therapy with a temporary blocking system to avoid the re-capture of these pigments to favor their elimination.
DOI: 10.1084 / jem.20171608
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