Follicle stimulating hormone (FSH) plays a key role in the ewe’s estrous cycle but understanding its continued importance during pregnancy is not well understood. Researchers have proposed a model theorizing that a cascade of hormones is responsible for pregnancy maintenance. Weems et al. proposed a model for placental progesterone production; theorizing progesterone secretion is intricately regulated by prostaglandin E (PGE), which in turn is regulated by pregnancy specific protein B (PSPB), which is regulated by estradiol-17β and further hypothesized FSH may be the regulatory hormone to placental secretion of estradiol-17β. However, minimal research has been done analyzing FSH and its role, if any, within the theorized model. We hypothesized FSHβ is the hormone responsible for regulating ovine placental estradiol-17β secretion with its cognate receptor (FSHR) present within placentomes.
Two methods of investigation were used to evaluate the expression of FSHβ and FSHR within the ovine placenta. Placentomes from gestational days 53 (n=4) and 101 (n=3) were collected under general anesthesia from Polypay sheep (n=7). Each placentome was manually separated into cotelydonary (fetal) and caruncular (maternal) samples. Real-time polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) were performed on each sample to evaluate the quantitative levels of FSHβ and FSHR. Results from RT-PCR and IHC were negative for FSHβ and equivocal for FSHR. However, these findings do not rule out FSHβ expression within the intercotyledonary regions of the placenta or endometrium. Evidence for the presence of FSHR within the placentome was inconclusive, but further studies with larger numbers and improved experimental models, are warranted.