Human Long-Term Deregulated Circadian Rhythm Alters Regenerative Properties of Skin and Hair Precursor Cells

The study by L'Oréal Research and Innovation, involving 20 women divided into diurnal workers and shift workers, showed that long-term circadian rhythm deregulation affects the regenerative properties of skin and hair precursor cells. The deregulated group exhibited altered expression of clock pathway proteins, decreased secretion of certain hormones, and a decrease in Sox2 mRNA expression, indicating changes in dermal papilla stem cells. An in vitro model using a casein kinase inhibitor showed a loss of clonogenic potential, which melatonin partially rescued. This research provided the first human evidence that circadian rhythm disruptions can impair skin and hair cell regeneration, but also suggested that these effects might be mitigated by clock pathway regulators like melatonin.