Photo of a woman holding a magnifying glass up to her skin
A closer look at skin shows that it has an 'internal clock' that helps protect it from environmental damage

Skin’s ‘internal clock’ helps protect it from environmental damage

17 October, 2013

Natural Health News — Human skin has an internal clock that helps it cope with UV radiation from the sun and other harmful environmental onslaughts.

A variety of cells in our body have internal clocks that help them perform certain functions depending on the time of day, and skin cells as well as some stem cells exhibit circadian (24 hour cycle) behaviours.

Previous research has shown that the skin does have its own internal rhythms that determine, for instance, that it is more likely to absorb what’s put onto it at 4pm than at 8am or you’re more likely to have an allergic skin reaction in the morning than later in the day (see our article The Secret Life of Your Skin for more on this).

This latest study has found that human skin stem cells deal with these environmental threats – some of which are also cyclical – by carrying out different functions depending on the time of day.

For instance, the researchers found that distinct sets of genes in human skin stem cells show peak activity at different times of day. Genes involved in UV protection become most active during the daytime to guard these cells while they proliferate – that is, when they duplicate their DNA and are more susceptible to radiation-induced damage.

New insights into premature ageing

By activating genes involved in UV protection during the day, these cells protect themselves against radiation-induced DNA damage. According to the researchers, the findings, published in the journal Cell Stem Cell, could pave the way for new strategies to prevent premature ageing and cancer in humans.

“Our study shows that human skin stem cells posses an internal clock that allows them to very accurately know the time of day and helps them know when it is best to perform the correct function,” says lead author Prof Salvador Aznar Benitah of the Centre for Genomic Regulation (CRG) in Barcelona. “This is important because it seems that tissues need an accurate internal clock to remain healthy.”

Benitah and his team have previously shown that animals lacking normal circadian rhythms in skin stem cells age prematurely, suggesting that these cyclical patterns can protect against cellular damage.

“We know that the clock is gradually disrupted in aged mice and humans, and we know that preventing stem cells from accurately knowing the time of the day reduces their regenerative capacity,” Benitah says.

Understanding more about the skin’s natural rhythms and how they become disrupted, he says, may help us find ways of preventing or delaying skin ageing as well as lead to new insights in to skin cancer.