THE EFFECT OF TOPICAL MINOXIDIL TREATMENT ON HAIR FOLLICULAR-GROWTH OF NEONATAL HAIRLESS DESCENDANTS OF MEXICAN-HAIRLESS DOGS

The effect of daily topical minoxidil treatment on hair growth was inv estigated in eight neonatal hairless pups. After 21 days of minoxidil treatment, hair growth occurred in the minoxidil-treated areas of each neonatal hairless pup. The numbers of hairs in the treated areas incr eased as compared with that in the areas treated with vehicle only. Hi stological findings revealed that the skin treated with minoxidil cont ained many hair follicles derived from epidermal ingrowths (hair germs ) projecting into the dermis. These hair follicles showed various stag es of neofolliculogenesis. After 31 days of treatment, terminal hair g rowth was observed. In the minoxidil-untreated areas, epidermal ingrow ths remained undifferentiated. These results revealed that hairless do gs developed hair growth reactions following minoxidil-treatment when such treatment is applied in the early neonatal period. Neonatal hairl ess pups are a useful model for evaluating the effectiveness of hair g rowth stimulators.