Importantly, testosterone in vitro increases the ability of beard cells to promote increased growth of other beard dermal papilla cells and keratinocytes (112–114) but decreased that of androgenetic alopecia dermal papilla cells from both men (114) and stump-tailed macaques (117). This implies that an autocrine mechanism is involved; androgen-mediated changes do involve alterations in dermal papilla cell numbers as well as the amount of extracellular matrix (96). A need to modify the autocrine production of growth factors could contribute to the slow androgenic response that often takes many years to reach full effect (19)
