Study Information and Results:
It is well known that sex hormones such as androgen and estrogen influence the hair growth in several animals. Aromatase is a member of cytochrome P-450 gene superfamily and catalyzes the conversion of androgen to estrogen, a rate-limiting step of estrogen biosynthesis.
Previous reports have suggested that aromatase exists in various extra-gonadal tissue as well as in gonadal tissue, and that the expression is regulated by alternative use of multiple exons 1 and promoters. In this study, in order to examine the involvement of aromatase in hair growth, we investigated the localization of aromatase at hair follicles in human and murine, and evaluated the role of this enzyme on hair re-growth using aromatase knockout mice.
Immunohistological technique for anagen hair follicles revealed that aromatase positive cells localized in outer root sheath tissue while were not observed in hair matrix, follicular papilla and epidermis. RT-PCR analysis of aromatase mRNA in plucked human hair suggested that aromatase transcripts were mainly composed of placenta-specific exon 1.
Next, we examined the effect of aromatase inhibitor on the hair re-growth of C3H mouse. e topical application of 1% aminoglutethimide significantly promotes the hair re-growth. Moreover, hair re-growth was significantly accelerated in aromatase knockout female mice in compared with wild type. Intriguingly, the color of re-grown hair of those mice was blacker than wild type and heterozygotes. Alteration of hair color was caused by the increase of melanin contents (total melanin and eu-melanin).
These results suggest that aromatase plays an important role on hair growth and melanin synthesis in hair follicles through the local synthesis of estrogen.