Commentary on: Hairless and the Polyamine Putrescine Form a Negative Regulatory Loop in the Epidermis

The commentary by Ramot and Vardy discusses a study by Luke et al. that explores the relationship between hairless (HR) protein and polyamines, specifically putrescine, in the regulation of hair growth. The study found that HR and putrescine form a negative regulatory feedback loop, which may influence hair cycling. High levels of ornithine decarboxylase (ODC1), which leads to increased putrescine, and overexpression of HR both result in hair loss and dermal cysts in mice, suggesting that controlled levels of ODC1 and putrescine are crucial for normal hair growth. The study also observed that overexpression of HR in normal human keratinocytes reduces ODC1 levels, while mutations in HR result in increased ODC1 levels. Additionally, ODC1 overexpression decreases HR levels, indicating that putrescine can repress HR levels. This connection between polyamine levels and HR, a known hair cycle regulator, suggests that polyamines likely function similarly in the hair follicle. The study also identifies potential putrescine targets that could play a role in hair cycling. The commentary highlights the importance of this study in understanding the complex regulation of hair growth and its implications for treating various hair disorders.