IGF1R signaling acts on the anagen to catagen transition in the hair cycle

Abstract

Insulin like growth factor 1 (IGF1) is important for skin development and homeostasis. However, overexpression and inactivation studies have produced variable findings regarding its role in hair follicle (HF) biology. Here, we studied a conditional and inducible knockout of the IGF1 receptor (IGF1R) in keratin 15-expressing bulge cells. Deletion of IGF1R after the development of the skin appendages in K15-IGF1R^KO mice showed no abnormalities in epidermal homeostasis. Numbers of bulge cells were lower in K15-IGF1R^KO mice than in controls, without consequences on wound healing, at least in young mice. K15-IGF1R^KO HFs entered anagen phase earlier than controls and showed a delay in the anagen/catagen switch. The expression of BMP-4 mRNA was inhibited in HFs from K15-IGF1R^KO. MED1 transcription was impaired in the epidermis of K15-IGF1R^KO mice. These findings suggest that IGF1R controls the hair cycle, partly through BMP-4 activation.

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