Abstract
It was suggested that human mesenchymal stromal cells might contain an intracrine enzyme machinery potentially able to synthesize the cell's own supply of dihydrotestosterone (DHT) from dehydroepiandrosterone (DHEA) pro-hormone produced in the adrenal cortex in the reticular zone, which is unique to primates. Indeed, 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 5alpha-reductase enzyme proteins were expressed in resting mesenchymal stromal cells (MSCs) in vitro. However, the 'bridging' enzymes 17beta-HSDs, catalysing interconversion between 17beta-ketosteroids and 17beta-hydroxysteroids, were not found in resting MSCs, but 17beta-HSD enzyme protein was induced in a dose-dependent manner by DHEA. Quantitative real-time polymerase chain reactions disclosed that this was mainly due to induction of the isoform 5 catalysing this reaction in 'forward', androgen-bound direction (P < 0.01). This work demonstrates that the MSCs have an intracrine machinery to convert DHEA to DHT if and when challenged by DHEA. DHEA as substrate exerts a positive, feed-forward up-regulation on the 17beta-hydroxy steroid dehydrogenase-5, which may imply that DHEA-DHT tailor-making in MSCs is subjected to chronobiological regulation.