Alcohol exposure impairs trophoblast survival and alters subtype-specific gene expression in vitro

Highlights

• Trophoblast cell survival in vitro was inhibited by ethanol.

• Ethanol reduced gene expression of trophoblast subtype-specific markers.

• Results suggest ethanol exposure can directly alter the viability of mature trophoblasts.

Abstract

Maternal alcohol consumption is common prior to pregnancy recognition and in the rat results in altered placental development and fetal growth restriction. To assess the effect of ethanol (EtOH) exposure on the differentiation of trophoblast stem (TS) cells, mouse TS lines were differentiated in vitro for 6 days in 0%, 0.2% or 1% EtOH. This reduced both trophoblast survival and expression of labyrinth and junctional zone trophoblast subtype-specific genes. This suggests that fetal growth restriction and altered placental development associated with maternal alcohol consumption in the periconceptional period could be mediated in part by direct effects on trophoblast development.

Introduction

Maternal perturbations during early pregnancy, including a low protein diet [1], [2], [3], undernutrition [4], [5], or alcohol (EtOH) exposure [6], [7], can result in fetal growth restriction and programming of adult disease. Alcohol is a common exposure during pregnancy, with current statistics being 47–58% of all pregnancies [11], [12]. Consumption of 5+ standard drinks has also been reported in the period prior to pregnancy recognition (14%) [11], [12]. In vivo rodent models of EtOH exposure during the periconception period [6] and intermittently throughout gestation [13], [14], have shown alterations to placental structure and expression of metabolic transporters. This is of interest as normal formation and function of the placenta is a critical determinant of fetal growth. Derived from the trophectoderm of the pre-implantation embryo, trophoblast cells contribute the majority of cells within the mature placenta and consist of a number of unique cell types with diverse morphologies and functions [8], [9]. The definitive chorioallantoic placenta is organised into two zones containing specialised trophoblast cell types; the junctional zone which has a structural and endocrine role, while the labyrinth zone contains the fetal and maternal vasculature and is the location of nutrient exchange [10]. Perturbations during pregnancy often result in modifications to placental growth [2], [5] and zonal allocation [6] in late gestation, however few studies have determined whether alterations to trophoblast differentiation in early pregnancy may be mediating these effects. We have previously reported that periconceptional EtOH exposure prior to implantation in the rat causes an increase in glycogen trophoblasts (GlyT) in the junctional zone during late gestation [6]. In addition, high dose (18–37% vol/vol) EtOH exposure from implantation until close to term (E6-E18) reduced invasion of trophoblast cells into the maternal decidua and caused labyrinth disorganisation [14]. However, it is unknown if placental defects are due to direct exposure of the trophoblast stem cells of the trophectoderm to EtOH within the uterine cavity, or via other indirect mechanisms such as interactions with altered uterine cells. Here we utilise an in vitro model of differentiating mouse trophoblast stem (TS) cells to examine the direct effects of EtOH on proliferation and differentiation.