SummaryDynamic changes in microRNAs in oocyte and cumulus cells before and after maturation may explain the spatiotemporal post-transcriptional gene regulation within bovine follicular cells during the oocyte maturation process. miR-20a has been previously shown to regulate proliferation and differentiation as well as progesterone levels in cultured bovine granulosa cells. In the present study, we aimed to demonstrate the function of miR-20a during the bovine oocyte maturation process. Maturation of cumulus–oocyte complexes (COCs) was performed at 39°C in an humidified atmosphere with 5% CO2 in air. The expression of miR-20a was investigated in the cumulus cells and oocytes at 22 h post culture. The functional role of miR-20a was examined by modulating the expression of miR-20a in COCs during in vitro maturation (IVM). We found that the miR-20a expression was increased in cumulus cells but decreased in oocytes after IVM. Overexpression of miR-20a increased the oocyte maturation rate. Even though not statistically significant, miR-20a overexpression during IVM increased progesterone levels in the spent medium. This was further supported by the expression of STAR and CYP11A1 genes in cumulus cells. The phenotypes observed due to overexpression of miR-20a were validated by BMP15 supplementation during IVM and subsequent transfection of BMP15-treated COCs using miR-20a mimic or BMPR2 siRNA. We found that miR-20a mimic or BMPR2 siRNA transfection rescued BMP15-reduced oocyte maturation and progesterone levels. We concluded that miR-20a regulates oocyte maturation by increasing cumulus cell progesterone synthesis by simultaneous suppression of BMPR2 expression.

中文翻译：

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miR-20a在牛卵丘细胞中的调控作用及其对卵母细胞成熟的贡献

总结成熟前后卵母细胞和卵丘细胞中微小RNA的动态变化可以解释卵母细胞成熟过程中牛卵泡细胞内的时空转录后基因调控。先前已显示 miR-20a 可调节培养的牛颗粒细胞中的增殖和分化以及孕酮水平。在本研究中，我们旨在证明 miR-20a 在牛卵母细胞成熟过程中的功能。卵丘-卵母细胞复合物 (COC) 的成熟是在 39°C 和 5% CO 的湿润气氛中进行的2在空气中。在培养后 22 小时，研究了 miR-20a 在卵丘细胞和卵母细胞中的表达。通过调节 miR-20a 在 COCs 中的表达来检查 miR-20a 的功能作用体外成熟（IVM）。我们发现 miR-20a 在卵丘细胞中的表达增加，但在 IVM 后卵母细胞中的表达减少。miR-20a的过表达增加了卵母细胞的成熟率。尽管没有统计学意义，但 IVM 期间的 miR-20a 过表达增加了用过的培养基中的孕酮水平。这进一步得到了以下表达的支持星星和CYP11A1卵丘细胞中的基因。由于 miR-20a 过表达而观察到的表型通过在 IVM 期间补充 BMP15 和随后使用 miR-20a 模拟物转染 BMP15 处理的 COC 来验证BMPR2siRNA。我们发现 miR-20a 模拟或BMPR2siRNA 转染挽救了 BMP15 降低的卵母细胞成熟和孕酮水平。我们得出结论，miR-20a 通过同时抑制卵丘细胞孕酮合成来调节卵母细胞成熟。BMPR2表达。