MESSENGER-RNA EXPRESSION OF STEROIDOGENESIS ENZYME SUBTYPES IN THE HUMAN PILOSEBACEOUS UNIT

In order to define the respective involvement of steroidogenesis enzym es subtypes in the control of hair follicle homeostasis, we evaluated, by semiquantitative RT/PCR, the expression levels of mRNAs coding for 17 beta-hydroxysteroid dehydrogenase type 1 and type 2, 3 beta-hydrox ysteroid dehydrogenase, Cyt.P450-aromatase, steroid 5 alpha-reductase type 1 and type 2 and 11 beta-hydroxysteroid dehydrogenase. These assa ys were performed for several components of the pilosebaceous unit (PS U); fresh plucked anagen hairs, sebaceous glands and primary culture o f dermal papilla, as well as other tissues involved in an active stero id metabolism (human testis, liver, placenta, prostate, ovary, uterus and adrenals) as controls. We found that plucked hair (i.e. mainly ker atinocytes from the inner and outer root sheaths) expressed: (1) very high levels of 17 beta-hydroxysteroid dehydrogenase type 2 correspondi ng to levels found in liver and placenta; (2) high levels of steroid 5 -alpha-reductase type 1 corresponding to levels found in testis, liver and ovary, and moderate levels of 17 beta-hydroxysteroid dehydrogenas e type 1, which corresponded to the expression in testis, prostate and uterus. In contrast, Cyt.P450-aromatase, 3 beta-hydroxysteroid dehydr ogenase and steroid 5 alpha-reductase type 2 were poorly expressed in the pilosebaceous unit as compared with other tissues. Interestingly, expression patterns of these enzymes in primary cultures of dermal pap illa were distinctive since 5 alpha-reductase type 1 and 11 beta-hydro xysteroid dehydrogenase were the only mRNA detected. Taken together, t hese results suggest that not only sebaceous gland but also outer root sheath keratinocytes may contribute, through the activity of the ster oid 5 alpha-reductase type 1, to the pathogenesis of androgen-dependen t alopecia.