The control of hair growth.

The hair follicle is one of a few human tissues containing stem cells. The stem cells are interspersed within the basal layer of the outer root sheath and in an area called the bulge. From this reservoir stem cells migrate to hair matrix and start to divide and differentiate. Their behavior is controlled by numerous cytokines produced by cells of the dermal papilla. Dermal papilla cells and some cells of the inner and outer sheaths of the follicle from androgen-dependent hairs have androgen receptors in their cytoplasm and nucleus. Androgens indirectly control hair growth by influencing the synthesis and release of cytokines from the dermal papilla cells. Drugs affecting hair growth belong to one of the following groups: cytotoxic drugs, antiandrogens and drugs acting on potassium channels. Further development of drugs selective for certain steps in the process of hair growth will enable more successful therapy of hair growth disorders.