The Vitamin D Receptor, the Skin and Stem Cells

The study explored the role of the vitamin D receptor (VDR) in skin and hair follicle biology, particularly its impact on keratinocyte function and hair cycling. Mice lacking functional VDRs developed normal initial hair coats but exhibited impaired hair follicle regeneration, leading to alopecia. This defect was attributed to issues in the keratinocyte component of hair follicles, independent of the receptor's ligand. The absence of a functional VDR impaired keratinocyte stem cell function, resulting in decreased bulge keratinocyte stem cells with age and abnormal differentiation into sebocytes. These findings highlighted the importance of VDR in maintaining hair follicle homeostasis and suggested that VDR mutations could lead to alopecia by disrupting normal hair cycle processes.