Human Hair Follicles Operate an Internal Cori Cycle and Modulate Their Growth via Glycogen Phosphorylase

The study revealed that human hair follicles (HFs) operated an internal Cori cycle and modulated their growth through glycogen phosphorylase (PYGL) activity. Anagen phase HFs, which are in active growth, contained high levels of glycogen in the outer root sheath (ORS), which decreased during the catagen phase. The research demonstrated that glycogen metabolism was active in ORS keratinocytes and that inhibiting PYGL stimulated HF growth and delayed catagen onset. This suggested that targeting glycogen metabolism could be a therapeutic approach for hair growth modulation.