We all need sunlight, but it’s very easy to get too much. Sunlight is the main source of the ultraviolet radiation we’re exposed to, and it can cause cancer - the two most common kinds of skin cancer, squamous and basal cell, are usually found on sun-exposed parts of the skin.
But there are several types of ultraviolet radiation. We have some idea of how each - UVA, UVB, and UVC rays impact the skin. But there is still debate about which causes increases in the fragility of skin tissue, and which does more damage that leads to wrinkles, something that’s debated in cosmetic industry research. Binghamton University researchers set out to learn more about how the sun’s rays damage skin, and whether UVA or UVB rays are worse.
"The cosmetics industry is a huge multibillion-dollar business, and they're all trying different things to add to their sunscreens to make them better at protecting skin," said Assistant Professor of Biomedical Engineering Guy K. German, who oversaw the research. "Up until this point, however, there have been a lot of studies about skin damage, but none that properly look at how UV affects the mechanical integrity of skin."
In this work, which was reported in the Journal of the Mechanical Behavior of Biomedical Materials, the researchers assessed female breast skin tissue samples, which they selected because it’s not usually exposed to sunlight. They exposed the tissue to various UV radiation wavelengths, and did not see any difference between the ranges of wavelengths - no UV was more or less harmful than another. They found that the level of damage was determined by how much UV energy was absorbed by the skin.
The scientists also learned how UV was affecting the skin; the UV rays weaken the bonds that link cells in the top layer of skin, called the stratum corneum. It does so by disrupting proteins in that layer, corneodesmosomes, which give the skin strength by holding its components together. After sunburn, the skin peels off because these adherent structures have been damaged.
"What we noticed when we applied more and more UV radiation is that the dispersion of these corneodesmosomes was increasing," explained Zachary W. Lipsky, a biomedical engineering graduate candidate. "They're supposed to be these nice little distinct points surrounding cells, but with more irradiation, they essentially look exploded, moving away from their position. We conclude that because of the disruption of these corneodesmosomes, it damages the skin's structural integrity."
The researchers are continuing this work; they want to know how deeper skin layers are impacted by UV radiation. For now, they are reminding people to protect themselves. Skin cancer is the most common type of cancer, and an estimated one in every five Americans will get skin cancer by the time they’re 70 years old.
"We're trying to push the message to use sunscreen not just for preventing skin cancer, but also to keep the integrity of your skin so you don't get infections or other problems," he said. "The stratum corneum is the first barrier to the outside environment, so we need to protect it against all these different bacteria and nasty stuff that can get into our bodies."
Sources: AAAS/Eurekalert! Via Binghamton University, Journal of the Mechanical Behavior of Biomedical Materials