GENETIC analyses of human skin are revealing more about what makes us look old. As well as throwing up ways to smooth away wrinkles, the studies may provide a quantifiable way to test claims made for skin products.
In the past, cosmetics companies relied on subjective assessments of skin appearance, and changes in its thickness, colour and protein composition, to evaluate the effectiveness of their products and work out the quantities of ingredients needed to get the best results. 鈥淚t was totally hit and miss,鈥� says Rosemary Osborne of in Cincinnati, Ohio.
Now skin researchers, including those at P&G, are starting to use DNA microarrays, common in the drugs industry, to measure the expression of thousands of genes in skin of different ages. 鈥淚t鈥檚 a way of finding mechanisms that were not known before,鈥� says , who studies skin genomics at Laval University in Quebec City, Canada.
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P&G recently compared gene expression in skin samples from the buttocks and forearms of 10 young and 10 older women. In older skin, they found a decrease in the expression of genes involved in cholesterol and fatty acid synthesis. More surprisingly, the opposite was true for genes associated with inflammation and other components of the immune system, suggesting that the immune system may play a role in ageing.
鈥淚n older skin there was an increase in the expression of genes associated with inflammation鈥�
Treating the older skin with niacinamide, which helps skin retain moisture, damped down expression of genes related to inflammation. 鈥淲e believe that improving the barrier results in a 鈥榬esignalling鈥� of key molecular components of the skin,鈥� says Jay Tiesman of P&G. Targeting this inflammation might one day help to keep wrinkles at bay. The findings will appear in the in July.
Identifying a 鈥済enetic signature鈥� of younger skin should also provide a benchmark for testing existing skin products. For example, P&G is measuring the effects on gene expression of a skin cream ingredient called pal-KT. Previous approaches suggested it increased production of structural skin proteins like collagen and laminin. Gene analysis indicates it also affects the expression of genes involved in wound healing.
P&G isn鈥檛 alone, cosmetics firm claims to have identified differences in the way genes in old and young skin respond to physical damage: changes in gene expression began just 6 hours after damage in young skin but took around 30 hours to kick in with older skin. What鈥檚 more, around 25 genes differ in their response to skin damage in young and old skin, says 尝鈥橭谤茅补濒.
Rigorous studies in people are needed to confirm that changing gene expression in older skin to match younger skin improves skin quality. 鈥淵ou could find that a molecule is up or down-regulated, but whether that relates to a consumer noticing a difference is a big jump,鈥� says Diona Damian at the University of Sydney, Australia.
If new tools become available for assessing skin products, this could force cosmetics companies to back up claims about their products with hard evidence.
鈥淚f you really want to bring cosmetics into the field of rigorous scientific evidence, genomics may be the best and most quantitative way of doing it,鈥� says Labrie.
