Exp Dermatol. 2002 Feb;11(1):52-8.

Type-1 steroid 5 alpha-reductase is functionally active in the hair follicle as evidenced by new selective inhibitors of either type-1 or type-2 human steroid 5 alpha-reductase.
Gerst C, Dalko M, Pichaud P, Galey JB, Buan B, Bernard BA.
L'Oréal Recherche Avancée, Hair Biology Group, Centre Recherche C. Zviak, Clichy, France.

Steroid 5 alpha-reductase catalyzes the reduction of testosterone (T) into the very potent androgen dihydrotestosterone (DHT). The different tissue expression patterns of the two isoforms of 5 alpha-reductase, namely type-1 and type-2 5 alpha-reductase (5 alpha-R1 and 5 alpha-R2, respectively), have prompted studies directed towards the synthesis of selective 5 alpha-R1 or 5 alpha-R2 inhibitors. In this present work, we have performed a structure/activity study on the inhibitory potential of indole carboxylic acids against hair follicle 5 alpha-reductase activity. We have demonstrated that this class of molecules were potent inhibitors of either 5 alpha-R1 or 5 alpha-R2 or both depending on (i) substituents in positions 4, 5 or 6 and (ii) the presence of a free carboxylic group. We have also found that only 5 alpha-R1 or 5 alpha-R1/R2 inhibitors were able to inhibit 5 alpha-reductase activity in plucked hairs from female volunteers or in freshly isolated female hair follicles, selective 5 alpha-R2 inhibitors being inactive.

5 alpha-reductase type 2 is constitutively expressed in the dermal papilla and connective tissue sheath of the hair follicle in vivo but not during culture in vitro.
Asada Y, Sonoda T, Ojiro M, Kurata S, Sato T, Ezaki T, Takayasu S.
Department of Dermatology, Oita Medical University, Japan. asada@oita-med.ac.jp

Recent studies suggest that 5 alpha-reductase type 2 (5 alpha R2) rather than 5 alpha R1 plays a key role in the pathogenesis of male-pattern baldness. To clarify the localization of the androgen receptor (AR), 5 alpha R1, and 5 alpha R2 in the hair follicle, we investigated the expression of the corresponding genes by RT-PCR using microdissected hair follicles. AR and 5 alpha R1 mRNAs were expressed in all portions of the hair follicle. By contrast, 5 alpha R2 mRNA was expressed only in mesenchymal portions that included the dermal papilla and connective tissue sheath, and hardly any was expressed in epithelial portions. The intensity of expression of these genes in each portion of the hair follicles did not differ between follicles from balding and nonbalding scalp. We also examined the expression of these genes in cultured fibroblasts derived from the dermal papilla and connective tissue sheath. Although expression of AR and 5 alpha R1 mRNAs was easily detected, there was no obvious expression of 5 alpha R2 mRNA in either type of cell. Type-specific inhibition of 5 alpha R activity by MK386 and MK906 confirmed these patterns of expression of 5 alpha R mRNA. Thus, the expression of 5 alpha R2 mRNA seems to be characteristic of freshly microdissected mesenchymal portions of the hair follicle, but such expression might not be maintained in culture.

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