Steroid metabolism and profile of steroidogenic gene expression in Episkin™: High similarity with human epidermis

Abstract

The skin is a well-recognized site of steroid formation and metabolism. Episkin™ is a cultured human epidermis. In this report, we investigate whether Episkin™ possesses a steroidogenic machinery able to metabolize adrenal steroid precursors into active steroids. Episkin™ was incubated with [ 14C]-dehydroepiandrosterone (DHEA) and 4-androstenedione (4-dione) and their metabolites were analyzed by liquid chromatography/mass spectrometry (LC/MS/MS). The results show that the major product of DHEA metabolism in Episkin™ is DHEA sulfate (DHEAS) (88% of the metabolites) while the other metabolites are 7α-OH-DHEA (8.2%), 4-dione (1.3%), 5-androstenediol (1.3%), dihydrotestosterone (DHT) (1.4%) and androsterone (ADT) (2.3%). When 4-dione is used as substrate, much higher levels of C19-steroids are produced with ADT representing 77% of the metabolites. These data indicate that 5α-reductase, 17β-hydroxysteroid dehydrogenase (17β-HSD) and 3α-hydroxysteroid dehdyrogenase (3α-HSD) activities are present at moderate levels in Episkin™, while 3β-HSD activity is low and represents a rate-limiting step in the conversion of DHEA into C19-steroids. Using realtime PCR, we have measured the level of mRNAs encoding the steroidogenic enzymes in Episkin™. A good agreement is found between the mRNAs expression in Episkin™ and the metabolic profile. High expression levels of steroid sulfotransferase SULT2B1B and type 3 3α-HSD (AKR1C2) correspond to the high levels of DHEA sulfate (DHEAS) and ADT formed from DHEA and 4-dione, respectively. 3β-HSD is almost undetectable while the other enzymes such as type 1 5α-reductase, types 2, 4, 5, 7, 8, and 10 17β-HSD and 20α-hydroxysteroid dehydrogenase (20α-HSD) (AKR1C1) are highly expressed. Except for UGT-glucuronosyl transferase, similar mRNA expression profiles between Episkin™ and human epidermis are observed.