A mechanism responsible for permanent hair loss as a result of chemotherapy is reported in Nature Communications this week. Using human hair follicles in a mouse model, the paper identifies chemotherapy-induced changes in hair follicle stem cells, which can lead to permanent hair loss.

Hair follicles, like many adult stem cell types, maintain a pool of cells for regeneration and can be damaged by chemotherapy. After hair loss due to chemotherapy, hair follicle stem cells can eventually recover and resume hair growth. However, some chemotherapy treatments lead to permanent baldness from loss of the stem cell pool.

Ohsang Kwon and colleagues transplanted human hair follicles onto hairless mice to establish a model for permanent chemotherapy-induced hair loss. The mice were treated with a two-step chemotherapy regimen associated with permanent hair loss in humans. The authors found the first step caused a wave of cell repopulation followed by massive cell death after the second phase of treatment. This prevented hair regeneration due to stem cell depletion. They provide evidence that the cells are more sensitive to DNA damage when proliferating, leading to problems with cell division and eventual death.

These findings shed light on the causes of permanent chemotherapy-induced hair loss and might be applicable to developing preventative treatments.