Nature: Sex hormones influence the activity of skin stem cells

The team tracked individual labelled epidermal cells in live animals over a period of five months. This made it possible to follow the fate of the cells and their descendants rather than simply compare tissue images taken at different time points.

The epidermis is constantly renewed: some cells retain the ability to self-renew, while others mature and gradually move towards the skin surface. The analysis confirmed the existence of an intermediate stage involving progenitor cells, which can still divide but only a limited number of times.

In females, daughter cells were more likely to behave in a coordinated manner: continuing to divide, maturing or leaving the basal layer at the same time. In males, their behaviour was less synchronized.

Comparisons of gene activity and additional experiments linked these differences to sex hormones. Male sex hormones promoted cell maturation and their exit from the basal layer of the epidermis.

So far, these patterns have only been demonstrated in mice. The authors believe that sex should be taken into account when studying skin regeneration, but whether the same mechanism operates in humans remains to be established.