The Expression of Activin-βA- and -βB-Subunits, Follistatin, and Activin Type II Receptors in Fallopian Tubes Bearing an Ectopic Pregnancy

Abstract

AbstractContext: Ectopic pregnancy is a major cause of maternal morbidity and mortality with increasing incidence worldwide.Objective: We investigated whether epithelia from Fallopian tubes (FTs) bearing an ectopic pregnancy differ from normal tubes in expression of TGF-β family and related proteins and their receptors.Methodology: Because it is not possible to collect FTs from women carrying a healthy pregnancy, we studied tissue collected at the time of hysterectomy for benign disease. Women were injected with human chorionic gonadotropin in the days leading up to hysterectomy to produce a state of pseudopregnancy. Pseudopregnancy status was confirmed by the presence of high serum progesterone levels and the decidualization of the endometrium. Fifteen FTs bearing ectopic pregnancy and six pseudopregnant tubes were collected and examined using immunohistochemistry and quantitative RT-PCR.Results: Immunohistochemistry demonstrated clear staining for the βA- and βB-subunits, type II receptor group comprising the activin type IIA and type IIB receptors, and follistatin, which increased in intensity from the isthmus to the ampulla in both models. However, the intensity of expression of these molecules was stronger in the ectopic pregnancy group when compared with the pseudopregnant group. Quantitative RT-PCR showed significant decrease in mRNA levels of βA-subunit, activin type IIA and IIB receptors, and follistatin in ectopic group (P < 0.05) but no changes in βB-subunit (P > 0.05). Overall, there was an apparent paradox of high concentration of protein but low mRNA expression.Conclusion: Activin-A may stimulate tubal decidualization and trophoblast invasion. A better understanding of the mechanism by which an embryo implants in the tubal epithelium may lead to improved methods for early diagnosis and/or management of ectopic pregnancy.