Skin has internal clock for repair and regeneration
26 July 2012
Human skin has an internal clock responsible for the
time-based steering of its repair and regeneration, among other things,
according to research published in the Proceedings of the Academy of
Our skin is one of the body’s essential organs and perhaps the
most versatile: besides representative, communicative and sensory
functions, it serves as our body’s boundary to the environment,
forms an active and passive barrier against germs and helps keeping
conditions constant for other important systems of the body, even
though environmental conditions can change drastically. Frost, heat,
sunlight and moisture — a variety of challenges for our skin — have
different effects depending on the time of day.
Prof. Achim Kramer’s research team from the field of
chronological biology at Charité — Universitätsmedizin Berlinand and
Dr. Thomas Blatt from the Skin Research Center in Hamburg have now
found out that skin adapts to these time-dependent conditions.
The researchers took cell samples (keratinocytes) from the
uppermost layer of skin from young, healthy test persons at various
times of the day. Analysis of numerous genes in the keratinocytes
showed that important factors for the regeneration and repair of
skin cells are regulated by a biological clock.
One of these factors, the molecule called the Krüppel-like-factor
(Klf9) slows down cell division in the keratinocytes: When the
researchers reduced the activity of this factor, they observed
faster growth in the skin cell cultures. On the other hand,
increased activity of Klf9 was connected with slower cell division.
At the same time, it was shown that the stress hormone cortisol also
controls the activity of Klf9 and can thus deploy a medical effect
on common skin diseases like psoriasis.
The job of the biological clock is to control the exact timing of
various processes like cell division, cell differentiation and DNA
repair in skin. Prof. Kramer is already looking to the future: “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.”
Florian Spörl, Thomas Blatt, Achim Kramer et al.: Krüppel-like
factor 9 is a circadian transcription factor in human epidermis that
controls proliferation of keratinocytes. In: Proceedings of the
Academy of Science (PNAS), Jul 3; 109(27):10903-8. DOI: