'All melanins are not born equal': Skin pigmentation research must consider ‘broader story’, says derma professor

Professor Desmond Tobin, director of the Charles Institute of Dermatology and full professor of dermatological science at the University College Dublin in Ireland, said research and analysis in the world of skin tone and pigmentation remained complex, with plenty of areas of improvement available to researchers and wider industry.

‘More robust assays’ needed​

“Clearly, there’s a very strong clinical unmet need for pigmentation disorders, not least for clinical disorders,”​ Tobin told attendees at last year’s IFSCC Congress in London, UK.

There was a responsibility, therefore, for researchers to come up with “the most robust assays” ​possible to “move to dial on some of these clinical unmet needs”.​

But there were challenges ahead, he said. Skin pigmentation research remained a “hugely complicated area to navigate”, ​particularly in terms of understanding the robustness of assays used and because melanocyte was “very difficult to work with”, ​the professor said.​

Most of today’s research also used cell lines not of human epidermis origin but rather based on mouse genetics, which was “not a great model for human epidermis” ​given mice were nocturnal animals versus sun exposed, he said. Studies using human epidermis cell models could also still be problematic, he said, because of how data was interpreted. “It’s very easy to be bamboozled in this area.”​

“…It’s also very easy to be mesmerised by the range of different experimental models – a snowstorm of different assays,” ​Tobin said, from botanical approaches through to human placental extracts. But, moving forward, he said researchers would do well to focus on human cells and primary epidermal melanocytes. “Take a second look at skin explants. I know there’s a lot of talk about 3D reconstructs but go back to the actual skin.”​

‘I think it’s a mistake to focus on tyrosinase inhibition’​

Over the past decade or so, Tobin said there had also been a lot of bias in skin pigmentation research, with a focus on tyrosinase inhibition.

“I think it’s a mistake to focus on tyrosinase inhibition,” ​the professor said. “[These studies] are addressing the first stage, albeit important, but there’s a lot more in melanogenesis beyond that point.”​

The process of making melanin in the skin, he said, was a “very protracted and convoluted process”​ of about five or six different steps, each of which had to be taken into close consideration during research. Beyond tyrosinase inhibition, this included looking at the transport of melanosome; how keratinocytes received melanin; and looking at melanin degradation and if there was really such a thing, he said.

Researchers also had to move beyond the “obsession with omics” ​that had, granted, provided lots of data, but had “perhaps not moved the dial on understanding pigmentation”, ​Tobin said. ​

‘All melanins are not born equal’​

In addition, it was vital to remember there were many different types of melanin, he said. “All melanins are not born equal. Our focus has been on the brown/black melanin, but there is the yellow/red melanin too.” ​And there remained very little knowledge on pheomelanin, for example, a lighter pigment found in red hair and concentrated in the redder areas of skin such as lips, specifically around how to measure it and how it was produced, he said.  

Researchers ought to also “be careful”​ when looking at skin pigmentation literature because it was largely Euro-centric and lacked broad data sets. “Remember, Africa has the highest level of genetic diversity in the world. We have to be very careful not to over-accentuate Euro-centric data.”​

Overall, it would be key that researchers looked at “the broader story”, ​he said, because skin pigmentation was a “multifactorial”​ topic.