From surgery to pharmacology to gene therapy: the past, present, and future of hair restoration.

The hair follicle is a complex structure containing many cell types that produce highly specialized proteins. These proteins govern the continuous cycling of the follicle through its stages of anagen, catagen, telogen, and exogen. Most common forms of alopecia result from the changes in the follicular cycling pattern and the morphology of the hair follicle. Hair restoration has traditionally been performed using scalp reduction techniques and the rearrangement of local hair-bearing flaps. Over the recent decades, hair transplantation has been the mainstay of hair restoration, whereas the pharmacological treatment of androgenic alopecia has halted the progression of hair loss. Over recent years, significant advances in the understanding of the biology and the molecular mechanisms of the follicle and its cycling have been made. This understanding, combined with new techniques for delivering molecules to the follicle, has made gene therapy for alopecia a possibility.