DKK2 and SOSTDC1 Cooperate to Initiate the First Catagen Phase of the Hair Follicle Growth Cycle

The study investigates the roles of DKK2 and SOSTDC1, two Wnt inhibitor genes, in the hair follicle growth cycle, particularly their involvement in initiating the first catagen phase. Human GWAS studies have linked these genes to male pattern baldness, and their expression is localized to the dermal papilla of human scalp hair follicles. In mice, both genes show strong expression in the dermal papilla at the onset of the first catagen phase and remain expressed through subsequent hair cycles. Mice lacking either Dkk2 or Sostdc1 alone had normal hair growth cycles, but co-deletion of both genes resulted in a significant delay in the onset of the first catagen phase. This indicates that DKK2 and SOSTDC1 are essential for the normal timing of the first catagen phase, suggesting that inhibiting Wnt inhibitors could potentially prolong the anagen phase for therapeutic purposes.