UMR PRC, CNRS, IFCE, INRA, Université de Tours, 37380, Nouzilly, France.
UMR BDR, ENVA, INRA, Université Paris-Saclay, 78350, Jouy-en-Josas, France.
J Ovarian Res. 2017 Nov 9;10(1):74. doi: 10.1186/s13048-017-0370-z.
Supplementation of bovine oocyte-cumulus complexes during in vitro maturation (IVM) with 1 μM of docosahexaenoic acid (DHA), C22:6 n-3 polyunsaturated fatty acid, was reported to improve in vitro embryo development. The objective of this paper was to decipher the mechanisms of DHA action.
Transcriptomic analysis of 1 μM DHA-treated and control cumulus cells after 4 h IVM showed no significant difference in gene expression. MALDI-TOF mass spectrometry analysis of lipid profiles in DHA-treated and control oocytes and cumulus cells after IVM showed variations of only 3 out of 700 molecular species in oocytes and 7 out of 698 species in cumulus cells (p < 0.01). We showed expression of free fatty acid receptor FFAR4 in both oocytes and cumulus cells, this receptor is known to be activated by binding to DHA. FFAR4 protein was localized close to the cellular membrane by immunofluorescence. Functional studies demonstrated that supplementation with FFAR4 agonist TUG-891 (1 μM or 5 μM) during IVM led to an increased blastocyst rate (39.5% ± 4.1%, 41.3% ± 4.1%), similar to DHA 1 μM treatment (39.2% ± 4.1%) as compared to control (25.2% ± 3.6%). FFAR4 activation via TUG-891 led to beneficial effect on oocyte developmental competence and might explain in part similar effects of DHA.
In conclusion, we suggested that low dose of DHA (1 μM) during IVM might activate regulatory mechanisms without evident effect on gene expression and lipid content in oocyte-cumulus complexes, likely through signaling pathways which need to be elucidated in further studies.
在体外成熟（IVM）过程中，向牛卵丘复合物中添加 1μM 的二十二碳六烯酸（DHA），一种二十二碳六烯酸（C22：6n-3 多不饱和脂肪酸），被报道可改善体外胚胎发育。本文的目的是破译 DHA 作用的机制。
4h IVM 后，1μM DHA 处理和对照卵丘细胞的转录组分析显示基因表达无显著差异。IVM 后，DHA 处理和对照卵母细胞和卵丘细胞的脂质谱 MALDI-TOF 质谱分析显示，卵母细胞中只有 700 种分子中的 3 种和卵丘细胞中的 698 种中的 7 种发生变化（p<0.01）。我们显示游离脂肪酸受体 FFAR4 在卵母细胞和卵丘细胞中均有表达，该受体已知通过与 DHA 结合而被激活。免疫荧光显示 FFAR4 蛋白定位于细胞膜附近。功能研究表明，在 IVM 期间补充 FFAR4 激动剂 TUG-891（1μM 或 5μM）可提高囊胚率（39.5%±4.1%、41.3%±4.1%），与 1μM DHA 处理（39.2%±4.1%）相似，而与对照（25.2%±3.6%）相比。通过 TUG-891 激活 FFAR4 对卵母细胞发育能力有有益作用，这可能部分解释了 DHA 的类似作用。
总之，我们认为在 IVM 期间添加低剂量的 DHA（1μM）可能会激活调节机制，而对卵丘复合物中的基因表达和脂质含量没有明显影响，可能通过需要在进一步研究中阐明的信号通路。
