孕期大气细颗粒物暴露对胎盘神经发育关键基因的表观遗传调控及与儿童认知能力的关联

Maternal exposure to fine particulate matter (PM2.5) during pregnancy has adverse effect on children’s neurodevelopment, but it is unknown whether the exposure affects children’s neurocognitive function. Based on the established large birth cohort, the present project is going to study the associations between maternal exposure to PM2.5 and neurocognitive development as follows. Firstly, we will estimate the individual daily PM2.5 exposure level during pregnancy based on monitoring data from Wuhan Air Automatic Monitoring System, and also calculate the mainly PM2.5 components exposure levels, such as heavy metal and polycyclic aromatic hydrocarbons, based on measured concentrations from the particulate filter samples. Secondly, we will follow up the children at 1 and 2 year-old and determine the neurocognitive function using Bayley scales of infant development. Then we can calculate the associations of maternal PM2.5 exposure with children neurocognitive function, and determine the critical window of exposure. In addition, we are going to explore the key role of methylation of placental genes which are involved in the process of PM2.5-associated neurocognitive dysfunction using a two-phase study design: 1) select placental genes whose methylation were altered by PM2.5 exposure using methylated chips in a relatively small population; 2) determine the methylation of the key genes in neurodevelopmental pathways in placenta in the large population of this birth cohort, and analyze the causal relationship of PM2.5 exposure-altered methylation-neurocognitive dysfunction using mediation analysis. The present project will be able to provide direct evidence on adverse effect on neurocognitive function resulted from maternal PM2.5 exposure, and clarify the role of altered methylation of placental genes in the effect of PM2.5 exposure on children’s neurocognitive function.

母亲孕期大气细颗粒物暴露可干扰儿童神经发育，但对儿童神经认知能力的影响目前并不清楚。本项目拟采用前瞻性队列研究设计，以已建立的出生队列中的母婴为研究对象，采用贝利婴幼儿发展量表测量儿童1岁和2岁时的神经认知能力；利用细颗粒物环境监测数据构建模型评估母亲妊娠不同时期细颗粒物暴露水平，并分析细颗粒物中重金属和多环芳烃组分浓度，研究孕期细颗粒物暴露与儿童认知能力的关联，确定作用敏感期；在此基础上，采用两阶段研究设计，首先用甲基化芯片筛选细颗粒物导致的胎盘基因甲基化改变，选择其中的神经发育关键通路基因在队列人群胎盘中检测后，与细颗粒物暴露和儿童认知水平进行中介效应分析，确定这些胎盘基因甲基化改变与细颗粒物暴露和儿童认知能力改变间的因果关系。本项目研究将为明确孕期大气细颗粒物暴露对儿童神经认知的影响提供直接证据，并阐明胎盘基因甲基化改变在细颗粒物暴露导致儿童神经认知改变中的作用。

母亲孕期大气细颗粒物暴露可干扰儿童神经发育，但对儿童神经认知能力的影响及可能机制目前并不清楚。本项目基于已建立的出生队列，采用前瞻性研究设计，以2013年到2015年招募的1329对母子对为研究对象，使用土地利用回归模型评估了母亲怀孕前及孕期细颗粒物暴露情况，采用贝利婴幼儿发展量表测量儿童2岁时的神经认知能力。发现怀孕前三个月及孕早期细颗粒物暴露每增加一倍，子代2岁时运动心理发育指数（PDI）分别降低7.96（95%CI: -9.80, -6.13）和7.93（95%CI: -9.70, -6.15）。孕早期细颗粒物暴露与子代2岁时心理发育指数（MDI）得分降低显著相关，但怀孕前3个月细颗粒物暴露与子代MDI的关联无统计学意义。此外，基于儿童出生时登记的居住地址信息，通过卫星遥感信息计算归一化植被指数（normalized difference vegetation index，NDVI）评估1312名儿童住宅周围绿地面积的暴露程度后发现：住宅周围绿地面积越大，儿童的神经认知发育测评指数越高。进一步研究发现，儿童周围绿地面积对其神经认知发育的影响可能是由于绿植降低了细颗粒物暴露的危害。中介效应模型结果显示细颗粒物暴露可降低18.7% (95% CI; 13.6%, 28.1%) 绿地接触暴露对儿童PDI的正向影响。在此基础上，运用全基因组关联分析方法，研究了母亲细颗粒物暴露导致的新生儿脐血DNA甲基化改变，分析脐血中与神经发育相关的关键基因的甲基化改变在孕妇细颗粒物暴露与2岁儿童认知能力关联中的介导作用。研究发现：孕早、中、晚期，和整个孕期细颗粒物暴露分别与脐血中249、1、4、59个CpGs位点甲基化水平改变相关（FDR<0.05）。分析基因功能，这些CpGs位点所在基因与甲状腺合成（path:hsa04918）、皮质醇合成和分泌（path:hsa04927），以及昼夜节律（path:hsa04710）通路有关。中介效应分析显示在孕早期、孕晚期和整个孕期分别有27、1和4个CpGs位点甲基化水平在孕妇细颗粒物暴露与2岁儿童PDI得分的关系中起到介导作用，贡献比例在19.2%~59.7%之间；有10、0、3个在细颗粒物暴露和子代MDI得分中起到介导作用，贡献比例在25.1%~67.5%。