The expression of MUC1 in human Fallopian tube during the menstrual cycle and in ectopic pregnancy

Ectopic pregnancy is a major cause of maternal morbidity and mortality with increasing incidence worldwide. We have investigated whether epithelia from Fallopian tubes (FTs) bearing an ectopic pregnancy differ from normal tubes in expression of MUC1.

Since 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 hCG in the days leading up to hysterectomy, and pseudopregnancy confirmed by the presence of high serum progesterone levels and the decidualization of the endometrium. FTs from the different stages of the menstrual cycle (n = 24), tubes bearing an ectopic pregnancy (n = 15) and pseudo-pregnant tubes (n = 6) were collected and examined using immunohistochemistry and quantitative RT-PCR.

MUC1 was present at the apical surface of the tubal epithelial cells throughout the menstrual cycle, but intracellular localization was minimal in the follicular phase, increasing to a maximum in the luteal phase. MUC1, including the glycoform recognized by antibody 214D4, was found at the apical surface of tubal epithelium in both the ectopic and pseudo-pregnant groups and the intracellular expression was much stronger in the pseudo-pregnant group than in the ectopic group. The 214D4 epitope was absent from tubal tissue adjacent to ectopic implants.

The decrease in MUC1 expression and altered glycosylation in tubal epithelium from ectopic pregnancy may reflect an increase in receptivity.