胚胎植入期外泌体小RNA介导妊娠识别和建立的研究

Precise ovary hormone secretion is a critical regulator of pregnancy establishment especially in embryo implantation. However, it remains a long-standing question that how the maternal body sense the local signal of embryo implantation and to fine-tune ovarian hormone secretion to support pregnancy. Here we found that small RNAs changes in serum is correlated with changes in implantation sites, suggesting that small RNAs induced from implantation sites are released into the serum, which has the potential to exert long-range regulation of other tissues. Moreover, we observed that serum exosomes extracted from post-implantation period could stimulate progesterone secretion of ovary corpus luteum, supporting our hypothesis that the small RNAs encapsulated in exosomes that are released from embryo implantation sites, and may act as important mediators to transport implantation signaling to ovary to stimulate hormonal release, thus initiate and maintain pregnancy. In this study, we will identify the implantation-derived critical exosomal small RNAs by small RNA-seq, and test their functions in stimulating corpus luteum hormones, as well as study the mechanism of these small RNAs in regulating hormone secretion. Furthermore, we will test our hypothesis in mouse model in vivo, and examine the exosomal small RNA changes in human serum (before and after pregnancy). This study aims to provide new insights to the mechanisms of pregnancy establishment as well as provide new methods for clinical use of exosomal small RNAs in pregnancy examinations.

在胚胎植入的起始阶段，植入信号如何由子宫局部传递给母体，并调控卵巢激素分泌以启动和维持妊娠是本领域内尚未解决的一个关键问题。申请人前期研究发现小鼠胚胎植入前后血清中的小RNA变化与植入位点小RNA变化呈现一致性，且植入后血清中携带小RNA的外泌体能够明显刺激卵巢黄体细胞产生维持妊娠的孕激素。鉴于外泌体小RNA是介导细胞/组织远距离交流的重要信号分子，我们推测：胚胎植入位点释放的小RNA可能通过外泌体经血液运输到卵巢等靶器官，进一步调控孕激素的产生以维持妊娠。本研究拟利用小鼠模型：1）筛选传递胚胎植入信息的外泌体小RNA；2）利用合成的关键小RNA体外转染卵巢黄体细胞，验证其对激素分泌的作用并研究机制；3）进行小鼠在体实验验证并收集临床妊娠血清进行检测，力图证实胚胎植入位点释放到循环系统的外泌体小RNA是传递子宫胚胎植入信息的重要信号分子，为早期妊娠识别和建立提供新的理论基础及临床诊疗依据。

我们通过对比分析胚胎植入前后血清外泌体小RNA表达谱及植入前后子宫小RNA表达谱，发现血清外泌体和子宫变化的miRNA和tsRNA有大部分重合，提示这些小RNA可能将子宫胚胎植入信息传递到血清。我们将血清外泌体和其中小RNA分别在体外转染分离的卵巢黄体细胞，发现能刺激黄体细胞分泌雌激素，证实外泌体和小RNA支持卵巢激素分泌的重要作用。我们通过建立“序贯植入”小鼠模型，通过在体实验进一步验证外泌体及小RNA传递胚胎植入信息。在这个课题进行的过程中，我们深刻认识到了外泌体和细胞外小RNA在传递机体信息中的重要作用。由此我们提出：母体妊娠早期的环境暴露信息可能通过外泌体和细胞外小RNA传递到胚胎，影响子代健康。此观点我们发表在Trends in Molecule Medicine（2017）。基于此我们建立了妊娠早期母体咖啡因暴露模型，发现胚胎植入前生理剂量的咖啡因暴露导致胚胎运输受阻，胚胎植入异常，造成妊娠流产，胎儿出生低体重。此工作发表在Biology of Reproduction （2018），并受邀对咖啡因暴露对妊娠结局和子代健康的影响进行了总结，相关综述发表在Trends in Endocrinology & Metabolism （2020）。受此项目支持还在Nature Cell Biology（2018）, Interface Focus (2019)等期刊发表相关论文。