Epidemiological studies have shown that cigarette smoking is a major risk factor for tubal ectopic pregnancy but the reason for this remains unclear. Here, we set out to determine the effect of smoking on Fallopian tube gene expression. An oviductal epithelial cell line (OE-E6/E7) and explants of human Fallopian tubes from non-pregnant women (n = 6) were exposed to physiologically relevant concentrations of cotinine, the principle metabolite of nicotine, and changes in gene expression analyzed using the Illumina Human HT-12 array. Cotinine sensitive genes identified through this process were then localized and quantified in Fallopian tube biopsies from non-pregnant smokers (n = 10) and non-smokers (n = 11) using immunohistochemistry and TaqMan RT-PCR. The principle cotinine induced change in gene expression detected by the array analysis in both explants and the cell line was significant down regulation (P<0.05) of the pro-apoptotic gene BAD. We therefore assessed the effect of smoking on cell turnover in retrospectively collected human samples. Consistent with the array data, smoking was associated with decreased levels of BAD transcript (P<0.01) and increased levels of BCL2 transcript (P<0.05) in Fallopian tube biopsies. BAD and BCL2 specific immunolabelling was localized to Fallopian tube epithelium. Although no other significant differences in levels of apoptosis or cell cycle associated proteins were observed, smoking was associated with significant changes in the morphology of the Fallopian tube epithelium (P<0.05). These results suggest that smoking may alter tubal epithelial cell turnover and is associated with structural, as well as functional, changes that may contribute to the development of ectopic pregnancy.
Galectin-1 and galectin-3 are abundantly expressed at implantation sites in the uterus, suggesting their involvement in the establishment of pregnancy. In this study, we examined the expression and localization of galectin-1 and galectin-3 in fallopian tubes from nonpregnant women, and in those presenting with tubal ectopic pregnancy. There was no significant difference in the expression of either galectin-1 (LGALS1) or galectin-3 (LGALS3) transcripts in the fallopian tube across the menstrual cycle. Their expressions in the fallopian tube were inversely correlated to each other (r = −0.5134, p < 0.0001) and differentially localized. Galectin-1 protein was abundant in the stroma of nonpregnant fallopian tubes, whereas galectin-3 was mainly localized to the epithelium, notably to the cilia of ciliated cells and the apical cytoplasm of secretory cells. In ectopic pregnancies, LGALS3 expression was significantly reduced (p < 0.0001), but LGALS1 expression did not change when compared to nonpregnant fallopian tubes collected during the mid-secretory phase. The percentage of fallopian tube epithelial cells expressing galectin-3 in cilia tended to be reduced (p = 0.0685), with an accompanying loss of a normal ciliary structure, while nuclear galectin-3 increased (p < 0.05) in ectopic pregnancies. Epithelial immunostaining for galectin-1 tended to be elevated in fallopian tubes from women with ectopic pregnancy. Coculture of human trophoblast origin SW71 cells significantly increased LGALS1 expression in human fallopian tube epithelial OE-E6/E7 cells, suggesting that trophoblast-derived products regulate LGALS1 expression in the oviductal epithelium. These findings imply a differential contribution of galectin-1 and galectin-3 in the homeostasis of human fallopian tubes and in the pathophysiology of ectopic pregnancy.
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