Research Resources: Comparative MicroRNA Profiles in Human Corona Radiata Cells and Cumulus Oophorus Cells Detected by Next-Generation Small RNA Sequencing

During folliculogenesis, cumulus cells surrounding the oocyte differentiate into corona radiata cells (CRCs) and cumulus oophorus cells (COCs), which are involved in gonadal steroidogenesis and the development of germ cells. Several studies suggested that microRNAs (miRNAs) play an important regulatory role at the post-transcriptional level in cumulus cells. However, comparative miRNA profiles and associated processes in human CRCs and COCs have not been reported before. In this study, miRNA profiles were obtained from CRCs and COCs using next generation sequencing in women undergoing controlled ovarian stimulation for IVF. A total of 785 and 799 annotated miRNAs were identified in CRCs and COCs, while high expression levels of six novel miRNAs were detected both in CRCs and in COCs. In addition, different expression patterns in CRCs and COCs were detected in 72 annotated miRNAs. To confirm the miRNA profile in COCs and CRCs, quantitative real-time PCR was used to validate the expression of annotated miRNAs, differentially expressed miRNAs, and novel miRNAs. The miRNAs in the let-7 family were found to be involved in the regulation of a broad range of biological processes in both cumulus cell populations, which was accompanied by a large amount of miRNA editing. Bioinformatics analysis showed that amino acid and energy metabolism were targeted significantly by miRNAs that were differentially expressed between CRCs and COCs. Our work extends the current knowledge of the regulatory role of miRNAs and their targeted pathways in folliculogenesis, and provides novel candidates for molecular biomarkers in the research of female infertility.

在卵泡发生（folliculogenesis）过程中，卵母细胞周围的卵丘细胞会分化为放射冠细胞（corona radiata cells, CRCs）与卵丘细胞（cumulus oophorus cells, COCs），二者均参与性腺类固醇合成与生殖细胞发育。已有多项研究证实，微小RNA（microRNAs, miRNAs）可在转录后水平对卵丘细胞发挥关键调控作用。然而，目前尚未有针对人类CRCs与COCs中miRNA表达谱及其关联调控过程的比较研究报道。
本研究采用下一代测序技术，对接受体外受精-胚胎移植（in vitro fertilization, IVF）控制性卵巢刺激的女性的CRCs与COCs进行miRNA表达谱分析。最终在CRCs与COCs中分别鉴定出785种和799种已注释miRNAs，同时在两类细胞中均检测到6种新型miRNAs的高表达。此外，另有72种已注释miRNAs在CRCs与COCs中呈现出显著差异的表达模式。
为验证CRCs与COCs中的miRNA表达谱，本研究通过实时定量PCR对已注释miRNAs、差异表达miRNAs及新型miRNAs的表达水平进行了验证。研究发现，let-7家族miRNAs可参与调控两类卵丘细胞群的多种生物学过程，且该过程伴随大量miRNA编辑现象。生物信息学分析显示，氨基酸代谢与能量代谢是CRCs与COCs间差异表达miRNAs的显著靶向通路。本研究拓展了当前对miRNAs及其靶向通路在卵泡发生中调控作用的认知，同时为女性不孕症研究中的分子生物标志物筛选提供了全新候选靶点。