Role of the ACTH/MC2R System in the Hair Cycle in Mice

This study investigated the role of the ACTH/MC2R system in the hair cycle using MC2R-/- mice, which lack the main receptor for ACTH. It was found that 15-week-old MC2R-/- mice were in the anagen phase, while MC2R+/+ mice were in the telogen phase. In five-day-old mice, hair growth occurred earlier in MC2R-/- mice compared to MC2R+/+ mice. Both age groups of MC2R-/- mice had higher levels of ACTH and alpha-melanocyte stimulating hormone in their blood. The hair cycle in 15-week-old MC2R-/- mice shifted to the telogen phase with a cGMP inhibitor and MC1R/MC5R inhibitor, while hair growth in five-day-old MC2R-/- mice was slowed by corticosterone. These findings suggested that the ACTH/MC2R system played a significant role in regulating the hair cycle.