IGF1R Signaling Acts on the Anagen-to-Catagen Transition in the Hair Cycle

The study explored the role of Igf1r signalling in the hair cycle, particularly the transition from anagen to catagen phases, using a murine model with Igf1r deletion in K15+ cells. The deletion led to a reduction in Igf1r mRNA and protein levels, affecting the hair cycle by causing an earlier entrance and prolonged anagen phase, delaying the transition to catagen. Despite these changes, the epidermis's morphology, proliferation, and differentiation remained unaffected, although the hypodermis was thicker during catagen with increased adipocyte numbers. The study concluded that Igf1r was crucial for hair cycle regulation, potentially interacting with Bmp-4 and Med1, but faced limitations due to incomplete deletion efficiency and challenges in demonstrating functional changes in bulge cells.