The skin is one of the body’s vital organs and possible one of the most versatile organ. Aside form its sensory, communicative and representative role, the skin acts as an active and passive barrier, protecting the body against germs, but also safeguarding inner organs and vital body systems from environmental conditions, such as heat, frost, moisture and sunlight, by ensuring a constant condition. Environmental factors expose the skin to numerous challenges, all with different effects depending on the time of the day.
Prof. Achim Kramer from the Charité in Berlin and Dr. Thomas Blatt from the Skin Research Center in Hamburg have now discovered that human skin has an internal clock, which has various roles, including being responsible for time-based cell repair and regeneration. First results from the basic research, which shows that skin adapts to these time-dependent conditions, are featured in the current edition of Proceedings of the Academy of Science (PNAS).
The researchers obtained cell samples (keratinocytes) from the stratum corneum, i.e. uppermost layer of skin from young, healthy test persons at different times of the day. After analyzing the keratinocytes, they discovered that important factors for skin cell regeneration and repair are controlled by a biological clock. They found that one role involved the molecule called the Krüppel-like-factor (Klf9), which slows down cell division in the keratinocytes.
When reducing Klf9’s activity, the team noted a more rapid growth in the skin cell cultures, whilst increasing the activity was linked to a slower cell division. They also found that the stress hormone cortisol simultaneously controls Klf9 activity, which means that Klf9 is involved or could be a marker for common skin diseases, such as like psoriasis.
The role of the biological clock regulates the precise timing of different processes, such as cell division and differentiation and DNA repair.
Prof. Kramer concludes: “If we understand these processes better, we could target the use of medication to the time of day in which they work best and have the fewest side effects.”
Written by Petra Rattue