Gene expression of 17 beta-hydroxysteroid dehydrogenase type 2 isozyme in primary cultures of human trophoblasts predicts different mechanisms regulating type 1 and type 2 enzymes

Abstract

Two 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) genes, types 1 and 2, have been cloned. The two isozymes show a 30% sequence homology but differ markedly in their kinetic properties. To date, the steroidogenic capacity of the placenta has been associated with syncytium formation. In this study, we have investigated 17 beta-HSD type 1 and type 2 gene expression during trophoblast differentiation in culture. We observed that term placenta and fetal cotyledons contain large amounts of both messenger RNAs (mRNAs). In culture, the type 1 gene is expressed concurrent with syncytium formation. However, type 2 expression is barely detectable in freshly isolated cytotrophoblasts and undetectable in syncytiotrophoblasts. Incubation of trophoblasts with progesterone and estradiol increased type 1 mRNA but did not restore 17 beta-HSD type 2 expression. 17 beta-HSD activities with substrates that differentiate the type 1 and type 2 enzymes correlated with the gene expression results. Type 1 activity decreased in freshly isolated trophoblasts by 2-fold and remained at these levels throughout the culture period. However, when compared with levels measured in term microsomes, type 2 activity decreased by 20-fold in freshly isolated cells and decreased again in culture by 5-fold. The expression pattern of 17 beta-HSD type 1 and type 2 activity in trophoblasts in culture suggests differing mechanisms regulate type 1 and type 2 mRNA levels.

Human type 2 17beta-hydroxysteroid dehydrogenase mRNA and protein distribution in placental villi at mid and term pregnancy

“…After Northern blot, membranes were hybridized at 42°C and washed under high stringency conditions [18]. The 17βHSD2 full-length cDNA fragment [14], and the gamma-actin cDNA 2 kb fragment were used to prepare the probes [30]. …”

“…The human placenta expresses mainly two 17βHSDs, types 1 and 2. Type 1 almost exclusively reduces E1 in E2 [14,15], whereas type 2 is reactive with E2 and testosterone with nearly comparable activities [16,17]. E2 synthesis in placenta depends on C19 steroid precursors dehydroepiandrosterone (DHEA) and its sulphate (DHEAS) from both maternal and foetal adrenal origin [1,2].…”

“…All the enzymes required in E2 synthesis are exclusively expressed by the syncytial layer (SL) delineating the floating villi [14,18,20]. E2 is secreted in both maternal and foetal circulations.…”

“…In two separate ontogeny studies, 17βHSD2 protein was first detected around weeks 7 [21] or 12 of pregnancy [20]. Then, the number of 17βHSD2-positive cells increases, reaching a plateau around week 19 of gestation and staying at that level until term [14,18,20]. Another study has shown that 17βHSD2 is also detected in the chorionic vein at 19 weeks of pregnancy [22].…”

Gene expression profile of androgen modulated genes in the murine fetal developing lung

“…Total RNA was extracted from fetal lung using Tri-reagent, a mixture of phenol and guanidine thiocyanate in a monophasic solution (Molecular Research Center, Cincinnati, OH) as described previously [15]. Each RNA sample was purified on a CsCl gradient as described [16], using a TLA 120.2 rotor in an Optima MAX centrifuge (Beckman, Mississauga, ON, Canada).…”