Regulation of the uteroplacental renin–angiotensin system in human pregnancy

A renin–angiotensin system (RAS) exists within the decidua and the placenta and has been shown to play a significant role in the regulation of trophoblast proliferation, invasion and migration, angiogenesis and the modulation of blood flow. As the RAS is crucial for the normal progression of pregnancy, it naturally follows then; that disruptions to the uteroplacental RAS during pregnancy may contribute to pregnancy complications such as intrauterine growth restriction (IUGR) and preeclampsia. Although many studies have linked changes in the RAS to these pathologies, our understanding of how the RAS is involved in these physiological changes is lacking, as are adequate medical interventions. This thesis attempts to address how the RAS is regulated within the uteroplacental unit. We explored the RAS in two trophoblast (i.e., placental) cell lines, HTR–8/SVneo and BeWo cells, to determine how they express the genes of the RAS and their proteins, in order to determine their value as models of the placental RAS. We found however, that HTR–8/SVneo cells expressed only the Angiotensin II (Ang II)/type 1 Ang II receptor (AT1R) pathway, while the BeWo cells expressed only the Angiotensin 1–7 (Ang 1–7)/Mas receptor pathway. Therefore these cell lines are not good models for placental RAS, but they are useful for exploring the regulation of RAS pathways within the placenta. Our aim was then to determine if we could induce the RAS pathways not expressed, in those cell lines that lacked them. We were also interested in the maternal decidua, as it is the main site of production of renin in the intrauterine tissues during human pregnancy and it plays a critical role in regulation of trophoblast invasion and placentation. We found that the expression of certain RAS genes within the decidua was sex specific. Decidua is a maternal tissue, yet the sex of the fetus determines the level of genes expression of the RAS pathway. This is extremely interesting since fetal sex is a major determinant of pregnancy outcome. We then showed that the sex specific differences in (pro)renin gene expression (REN) was not due to maternal sex steroid exposure. In fact, ex vivo, prorenin protein, along with several other RAS genes were expressed in a sex specific manner. Based on these observations, we were interested in determining how the sex of the fetus could affect RAS gene expression of a maternal tissue. In addition, we wanted to show whether this sex difference could be attenuated with cAMP stimulation. In conclusion, this thesis shows the RAS pathways within two trophoblast cell lines, establishes a decidual explant model that expresses the RAS and demonstrates that the decidual RAS is sexually dimorphic and finally discusses how these findings may contribute to our understanding of the role fetal sex plays in determining pregnancy outcome.