Epithelial Wnt Ligand Secretion Is Required for Adult Hair Follicle Growth and Regeneration

In 2013, Myung PS and colleagues conducted a study on the role of Wnt ligand secretion in hair follicle growth and regeneration. They focused on the gene Wntless (Wls), which is necessary for the secretion of Wnt ligands by Wnt-producing cells. They found that the expression of Wls in the hair follicle was low or undetectable during the telogen phase, but markedly upregulated during the early anagen phase. When they deleted Wls expression in the basal layer of the epidermis or hair follicle stem cells (HFSCs), most hair follicles were arrested in the telogen phase, with over 90% of hair follicles showing telogen arrest when Wls was deficient in HFSCs. Despite this, the expression of HFSC markers was maintained in Wls-deficient mice, suggesting that Wnts are not required for the preservation of HFSCs but are critical for the onset of the anagen phase. The study concluded that Wnt ligand secretion by hair follicle epithelial cells is important for the onset of the anagen phase and hair regeneration, providing potential new targets for the treatment of hair disorders like alopecia.