Researchers in Japan have shed yet more light on the topic, discovering a new mechanism by which dividing cells can drive hair follicles to exhaustion, subduing their regenerative abilities as we age.

The research was carried out by scientists at Tokyo Medical and Dental University and the University of Tokyo, who set out to explore the way hair follicle stem cells help us grow new hair, and the reasons why that important relationship can break down.

The sustainability of our hair follicle stem cells is reliant on a healthy combination of two types of cell division. In cyclic symmetric cell division, the hair follicle stem cells are split into two cell types with the same fate, while in asymmetric cell division, they are split into a differentiating cell along with a separate, self-renewing stem cell. These two cycles work in concert to keep the population of hair follicle stem cells alive and able to regenerate hair. By the same token, they can lead to their death when they don't work as they should.