Toxicogenomics analysis of placenta samples from mice exposed to different doses of BPA. Mus musculus

Bisphenol A (BPA) is a widespread Endocrine Disrupter mainly used in food contact plastics. Several evidences support BPA adverse effects, especially on susceptible groups such as pregnant women. The present study considered placental development - relevant for pregnancy outcomes and fetal nutrition/programming - as a potential target of BPA. Pregnant CD-1 mice were administered per os with vehicle, 0.5 (BPA05) or 50 mg/kg (BPA50) body weight (bw)/die of BPA, from gestational day (GD) 1 to GD11. At GD12, BPA50 induced significant degeneration and necrosis of giant cells, increased vacuolization in the junctional zone in absence of glycogen accumulation and reduction of the spongiotrophoblast layer. BPA05 induced a significant nuclear accumulation of β-catenin in trophoblasts of the labyrinthine and spongiotrophoblast layers, supporting an activation of the Wnt/β-catenin pathway. Transcriptomic analysis indicated a BPA05 promotion and a BPA50 inhibition of blood vessels development and branching supported by the morphological observation of decreased and increased total vessels area in the labyrinth layers upon BPA05 and BPA50 treatments, respectively, with BPA50 also inducing a decrease in vessels number. These mechanisms involve, respectively, CREB and Wnt/β-catenin pathways for BPA05 and AhR/ARNT pathway for BPA50, as deducted by the transcription factor binding analysis. These results show that BPA differently affects mouse placental development depending on the dose level. In particular, the 0.5 mg/kw bw, in the range of dose level used to set the Tolerable Daily Intake, may elicit not negligible alterations whose relevance for human health has to be carefully evaluated. Overall design: Three conidtions experiment: Control, BPA 0.5 mg/kg bw die; BPA 50 mg/kg bw die. Biological replicates: three control replicates; four replicates per treatment. Technical replicates: 2 (dye swap) per biological replica双酚A（Bisphenol A, BPA）是一种广泛分布的内分泌干扰物（Endocrine Disrupter），主要应用于食品接触类塑料制品的生产。多项研究证据表明，BPA可产生多种不良生物学效应，尤其对孕妇等易感人群的危害尤为突出。本研究将与妊娠结局及胎儿营养/编程密切相关的胎盘发育（placental development），确定为BPA的潜在作用靶点。 选用妊娠CD-1小鼠，自妊娠第1天（gestational day, GD）1至妊娠第11天（GD11），经口给予溶媒对照、0.5 mg/kg体重/天（记为BPA05组）或50 mg/kg体重/天（记为BPA50组）的BPA染毒处理。 于GD12时进行样本采集与形态学观察，结果显示BPA50组可诱导胎盘巨细胞（giant cells）发生显著变性与坏死，使胎盘交界区（junctional zone）出现明显空泡化且无糖原积累（glycogen accumulation），同时导致海绵滋养层（spongiotrophoblast layer）厚度降低。BPA05组则可使迷路层（labyrinthine layer）与海绵滋养层的滋养细胞中β-连环蛋白（β-catenin）发生显著核聚集，提示Wnt/β-连环蛋白（Wnt/β-catenin）通路被激活。 转录组学分析（transcriptomic analysis）结果显示，BPA05组可促进血管发育与分支（blood vessels development and branching），而BPA50组则产生抑制作用；该结论与形态学观察结果一致：BPA05组小鼠胎盘迷路层的血管总面积降低，BPA50组则相反出现升高，且BPA50组同时伴随血管数量减少。 通过转录因子结合位点分析可知，上述剂量依赖性效应分别由环腺苷酸应答元件结合蛋白（CREB）通路、Wnt/β-连环蛋白通路（BPA05组）以及芳香烃受体/芳烃受体核转位蛋白（AhR/ARNT）通路（BPA50组）介导。 本研究结果表明，BPA可依据暴露剂量的不同对小鼠胎盘发育产生差异化影响。其中0.5 mg/kg体重/天的暴露剂量处于每日可耐受摄入量（Tolerable Daily Intake）的设定剂量范围内，该剂量可引发不容忽视的胎盘发育异常，其对人类健康的潜在相关性仍需开展审慎评估。 总体实验设计：本实验设置三组处理条件：空白对照组、BPA 0.5 mg/kg体重/天组、BPA 50 mg/kg体重/天组。生物学重复：对照组设置3次生物学重复，各处理组各设置4次生物学重复；技术重复：每个生物学重复设置2次技术重复（采用染料互换法）。