Ovarian follicular fluid (FF) is a dynamic environment that changes with the seasons, affecting follicle development, ovulation, and oocyte quality. Cells in the follicles release tiny particles called extracellular vesicles (EVs) containing vital regulatory molecules, such as microRNAs (miRNAs). These miRNAs are pivotal in facilitating communication within the follicles through diverse signaling and information transfer forms. EV-coupled miRNA signaling is implicated to be associated with ovarian function, follicle and oocyte growth and response to various environmental insults. Herein, we investigated how seasonal variations directly influence the ovulatory and anovulatory states of ovarian follicles and how are they associated with follicular fluid EV-coupled miRNA dynamics in horses. Ultrasonographic monitoring and follicular fluid aspiration of preovulatory follicles in horses during the anovulatory (spring: non-breeding) and ovulatory (spring, summer, and fall: breeding) seasons and subsequent EV isolation and miRNA profiling identified significant variation in EV-miRNA cargo content. We identified 97 miRNAs with differential expression among the groups and specific clusters of miRNAs involved in the spring transition (miR-149, -200b, -206, -221, -328, and -615) and peak breeding period (including miR-143, -192, -451, -302b, -100, and let-7c). Bioinformatic analyses showed enrichments in various biological functions, e.g., transcription factor activity, transcription and transcription regulation, nucleic acid binding, sequence-specific DNA binding, p53 signaling, and post-translational modifications. Cluster analyses revealed distinct sets of significantly up- and down-regulated miRNAs associated with spring anovulatory (Cluster 1) and summer ovulation–the peak breeding season (Clusters 4 and 6). The findings from the current study shed light on the dynamics of FF-EV-coupled miRNAs in relation to equine ovulatory and anovulatory seasons, and their roles in understanding the mechanisms involved in seasonal shifts and ovulation during the breeding season warrant further investigation.

中文翻译：

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对马卵泡液细胞外囊泡 miRNA 表达动力学的季节性影响


卵巢卵泡液 （FF） 是一种随季节变化的动态环境，影响卵泡发育、排卵和卵母细胞质量。卵泡中的细胞释放称为细胞外囊泡 （EV） 的微小颗粒，其中包含重要的调节分子，例如 microRNA （miRNA）。这些 miRNA 在通过不同的信号转导和信息传递形式促进卵泡内的通讯方面发挥着关键作用。EV 偶联的 miRNA 信号转导与卵巢功能、卵泡和卵母细胞生长以及对各种环境损伤的反应有关。在此，我们研究了季节性变化如何直接影响卵巢卵泡的排卵和无排卵状态，以及它们如何与马卵泡液 EV 偶联的 miRNA 动力学相关。在无排卵 （春季：非繁殖） 和排卵 （春季、夏季和秋季：繁殖） 季节对马排卵前卵泡进行超声监测和卵泡液抽吸，以及随后的 EV 分离和 miRNA 分析确定了 EV-miRNA 货物含量的显着变化。我们鉴定了 97 个 miRNAs，这些 miRNAs 在参与春季转变 （miR-149 、 -200b、 -206、 -221、 -328 和 -615） 和繁殖高峰期 （包括 miR-143 、 -192 、 -451、 -302b 、 -100 和 let-7c） 的组和特异性簇之间具有差异表达。生物信息学分析显示各种生物学功能的富集，例如转录因子活性、转录和转录调控、核酸结合、序列特异性 DNA 结合、p53 信号传导和翻译后修饰。 聚类分析揭示了与春季无排卵（聚类 1）和夏季排卵（繁殖高峰季节（聚类 4 和 6）相关的不同显著上调和下调的 miRNA。当前研究的结果阐明了 FF-EV 偶联 miRNAs 与马排卵和无排卵季节相关的动力学，以及它们在理解繁殖季节季节变化和排卵所涉及的机制中的作用值得进一步研究。