Trends in Human Hair Growth and Alopecia Research pp 105-116 | Cite as
Pharmacological aspects of hair follicle growth
Abstract
The potent hypertrichotic effect of minoxidil opened a new field in both pharmacological study and clinical application of the drugs on hair growth. Topically applied minoxidil is effective for hair growth in the early stage of androgenetic alopecia and, to some extent, for the treatment of alopecia areata. Using the macaque model of androgenic alopecia, we studied sequential morphometric analysis (folliculogram) of the hair follicles after treatment with topical minoxidil as well as antiandrogen. Minoxidil also acts as a mitotic stimulator of the follicular cells in the secondary germ, follicular sheath, and bulbar matrix. Consequently, the vellus follicles in the bald scalp enlarge and transform to the terminal follicles. Minoxidil also induced a cyclic acceleration of rat hair follicles. The mechanism of this follicular growth will be discussed with the similar phenomenon caused by the activation of protein kinase C in the skin by phorbol ester. Topical applications of 4-MA (an inhibitor of 5α-reductase) on the bald scalp of macaques prevented the development of baldness during periadolescent age. Analysis of folliculograms revealed that the size and distribution pattern of cyclic follicles showed no change in 4-MA-treated scalps over 2 years, while the folliculograms of controls changed to a typical bald pattern. The drug also induced a substantial decrease of 5α-reductase activity in the scalp skin. These results strongly suggest that dihydrotestosterone is a potent androgen to trigger the regressive change in genetically linked hair follicles.
Keywords
Hair Follicle Hair Growth Outer Root Sheath Dermal Papilla Cell Anagen PhasePreview
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