Steroid hormones play a crucial role in supporting a successful pregnancy and ensuring proper fetal development. The placenta is one of the principal tissues in steroid production and metabolism, expressing a vast range of steroidogenic enzymes. Nevertheless, a comprehensive characterization of steroidogenic pathways in the human placenta and potential developmental changes occurring during gestation are poorly understood. Furthermore, the specific contribution of trophoblast cells in steroid release is largely unknown. Thus, this study aimed to (i) identify gestational age-dependent changes in the gene expression of key steroidogenic enzymes and (ii) explore the role of trophoblast cells in steroid biosynthesis and metabolism. Quantitative and Droplet Digital PCR analysis of 12 selected enzymes was carried out in the first trimester (n = 13) and term (n = 20) human placentas. Primary trophoblast cells (n = 5) isolated from human term placentas and choriocarcinoma-derived cell lines (BeWo, BeWo b30 clone, and JEG-3) were further screened for gene expression of enzymes involved in placental synthesis/metabolism of steroids. Finally, de novo steroid synthesis by primary human trophoblasts was evaluated, highlighting the functional activity of steroidogenic enzymes in these cells. Collectively, we provide insights into the expression patterns of steroidogenic enzymes as a function of gestational age and delineate the cellular origin of steroidogenesis in the human placenta.

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-related condition characterized by increased maternal circulating bile acids (BAs) having adverse fetal effects. We investigated whether the human placenta expresses specific regulation patterns to prevent fetal exposition to harmful amounts of BAs during ICP. Using real-time quantitative PCR, we screened placentae from healthy pregnancies (n = 12) and corresponding trophoblast cells (n = 3) for the expression of 21 solute carriers and ATP-binding cassette transporter proteins, all acknowledged as BA- and/or cholestasis-related genes. The placental gene expression pattern was compared between healthy women and ICP patients (n = 12 each). Placental SLCO3A1 (OATP3A1) gene expression was significantly altered in ICP compared with controls. The other 20 genes, including SLC10A2 (ASBT) and EPHX1 (EPOX, mEH) reported for the first time in trophoblasts, were comparably abundant in healthy and ICP placentae. ABCG5 was undetectable in all placentae. Placental SLC10A2 (ASBT), SLCO4A1 (OATP4A1), and ABCC2 mRNA levels were positively correlated with BA concentrations in ICP. Placental SLC10A2 (ASBT) mRNA was also correlated with maternal body mass index. We conclude that at the transcriptional level only a limited response of BA transport systems is found under ICP conditions. However, the extent of the transcriptional response may also depend on the severity of the ICP condition and the magnitude by which the maternal BA levels are increased.

Recent advances in analytical methods have revolutionized our understanding of steroid biochemistry. The emergence of novel steroids such as 11-oxy androgens and 11-oxy progesterones has necessitated a reevaluation of steroid biosynthesis and metabolism within the maternal-placental-fetal unit. In this study, we employed a validated liquid chromatography high-resolution mass spectrometry method to quantify 51 steroids in paired maternal serum, neonatal serum, and placenta samples from 37 healthy pregnancies. Additionally, we characterized steroid release in various placental models, including human placenta perfusion, explants, and primary trophoblast cells isolated from human term placenta. Our findings emphasize the predominance of keto-derivatives of androgens in the placenta compared to hydroxylated forms, which are dominant in maternal serum and neonatal serum. We also observed high levels of classic and novel progesterones in the placenta and across all models, with significant release on the maternal side. These results suggest that the placenta possesses an active enzymatic machinery capable of producing and metabolizing novel progesterones. Furthermore, we demonstrated that the catalytic activity of 11β-hydroxysteroid dehydrogenase type 2 extends beyond cortisol regulation to hydroxylated androgens, highlighting its significance in the broader context of steroid metabolism within the maternal-placental-fetal unit. These findings contribute to our understanding of placental physiology and impact on fetal development.