Study reveals new mechanism by which hair follicles lose their regenerative capabilities Hair grows from stem cells residing in hair follicles. During aging, the capability of hair follicles to grow hair is successively lost, leading to hair thinning and ultimately hair loss. In a new study, researchers from Tokyo Medical and Dental University (TMDU) and the University of Tokyo identified a novel mechanism by which hair follicles lose their regenerative capabilities. Hair follicles are mini-organs from which new hair constantly grows. The basis for new hair growth is the proper function of hair follicle stem cells (HFSCs). HFSCs undergo cyclic symmetric and asymmetric cell divisions (SCDs and ACDs).