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Keywords:

  • androgenetic alopecia;
  • androgen receptor knockout mouse;
  • hair cycle

Summary

Background  Androgens cause regression of human hair follicles in the parietofrontal scalp, but the precise mechanisms by which they do so are unknown. Although many investigators have elucidated the effect of androgens on hair growth by using rodents and other animals, some of the evidence is conflicting.

Objectives  To investigate the effect of androgens on mouse hair regrowth and hair cycle by using androgen receptor knockout (ARKO) mice.

Methods  We examined the effects of dihydrotestosterone (DHT) on hair regrowth by using ARKO mice and wild-type (WT) littermates, compared the hair cycles in ARKO mice and WT littermates by histology and histomorphometry, and measured hair length and thickness in ARKO mice and WT littermates.

Results  DHT inhibited the hair regrowth of WT mice but not that of their ARKO littermates. The anagen phase in the second hair cycle was longer in ARKO mice than in their WT littermates. The hair of ARKO mice was longer and thicker than that of their WT littermates.

Conclusions  Androgens inhibit hair growth in mice, and this inhibition might be caused by androgen–androgen receptor signals.