Controlled ovarian hyperstimulation (COH) is used in assisted reproductive techniques such as in vitro fertilization (IVF). However, the process of COH has been shown to decrease endometrial receptivity for the implanting blastocyst. The factors which cause this decrease in uterine receptivity remain unclear. A newly developed rat OH model is currently being used to uncover the factors which alter endometrial receptivity during OH. It has previously been shown in both rat and human models that glycoproteins such as mucins on the apical plasma membrane of uterine epithelial cells (UECs) inhibit blastocyst implantation.
Mucins are highly glycosylated transmembrane proteins present on the uterine epithelium where they sterically hinder blastocyst implantation due to their highly branched nature. The aim of this study is to compare levels of mucin expression in UECs during the period of implantation in normal and ovarian OH pregnancies in the rat.
To induce OH, female rats with regular oestrous cycles were superovulated with an intraperitoneal (IP) injection of 20IU PMSG followed by another IP injection of 20IU hCG 24 hours later. Rats were then mated overnight. The pregnant rats were euthanized and their uteri collected and analyzed using western blotting techniques and immunohistochemistry.
We found a decrease in Mucins 1 and 4 in UECs at the time of fertilization and implantation in OH compared to normal pregnancy. This suggests that mucins may be altered as a result of OH and this may contribute to the altered receptivity resulting from fertility drugs.