A Meeting of Two Chronobiological Systems: Circadian Proteins Period1 and BMAL1 Modulate the Human Hair Cycle Clock

The study demonstrated that human hair follicles (HFs) exhibit circadian changes in the expression of core clock genes (CLOCK, BMAL1, and Period1) and clock-controlled genes (c-Myc, NR1D1, and CDKN1A) even in the absence of central clock influences. It was found that the expression of Period1 is dependent on the hair cycle phase. Knockdown experiments showed that reducing BMAL1 or Period1 in anagen HFs significantly prolonged the anagen phase. This indicated that peripheral core clock genes play a role in modulating HF cycling, identifying BMAL1 and Period1 as potential therapeutic targets for influencing human hair growth.