Melanogenesis During the Anagen-Catagen-Telogen Transformation of the Murine Hair Cycle

The study analyzed melanin synthesis in the hair cycle of C57 BL-6 mice, finding that melanogenesis is closely linked to the anagen (growth) phase and stops during catagen (regression) and telogen (resting). The researchers used electron paramagnetic resonance spectroscopy (EPR) to measure melanin synthesis and observed a sharp decline in melanin-associated EPR signals, tyrosinase and dopachrome tautomerase activities, and the concentration of melanogenesis-related proteins during the transition from anagen to catagen. The lowest levels of these markers were found in the telogen phase. Only eumelanin was detected in all stages of the hair cycle. The study revealed that the cessation of melanogenesis begins in mid anagen VI, earlier than previously thought, with a significant decrease in tyrosinase activity marking the start of catagen. These findings suggest that the end of melanogenesis is a gradual and stochastic process, and the measured parameters can serve as markers for the end of the anagen phase and the onset of catagen.