Autophagy plays an important role in mammalian oocyte maturation and early embryonic development and rapamycin is well known for inducing autophagy. Although previous studies have reported the effects of rapamycin on oocytes in vitro maturation (IVM) in different species, few studies have been reported on the role of rapamycin in yak oocytes IVM and embryonic development. Therefore, the objective of this study was to examine the effect of rapamycin treatment on yak oocytes IVM and early embryonic development. Specifically, immature yak oocytes during IVM or parthenogenetic (PA) embryos were treated with different rapamycin concentrations to select an optimal dose. Then evaluated its effect on maturation rates, cleavage, and blastocyst formation rates, mitochondrial membrane potential, ROS levels. Related genes and proteins expression in matured oocytes and blastocysts were also evaluated. The results show that 10 nM rapamycin treatment during IVM significantly improved oocyte maturation rates of oocytes and blastocyst formation rates. Treatment with 10 nM rapamycin reduced ROS level but increased mitochondrial membrane potential. Correspondingly, mRNA and protein expressions of LC3, Beclin-1, and Bcl-2 up-regulated while Bax down-regulated in matured yak COCs. When parthenogenetic embryos were treated with different rapamycin concentrations, 10 nM rapamycin treatment showed higher 8-cell and blastocyst formation rates. Also, CDX2, POU5F1, SOX2, and Nanog levels in blastocysts were upregulated. In summary, our findings demonstrate that rapamycin treatment improves oocytes maturation probably by increasing mitochondrial membrane potential, reducing ROS levels, and regulating the apoptosis in mature yak oocytes. Rapamycin treatment also improves embryonic developmental competence in the yak.

自噬在哺乳动物卵母细胞成熟和早期胚胎发育中起重要作用，雷帕霉素以诱导自噬而闻名。虽然之前的研究报道了雷帕霉素对不同物种卵母细胞体外成熟（IVM）的影响，但关于雷帕霉素在牦牛卵母细胞IVM和胚胎发育中的作用的研究报道很少。因此，本研究的目的是检查雷帕霉素治疗对牦牛卵母细胞IVM和早期胚胎发育的影响。具体而言，IVM 或孤雌 (PA) 胚胎期间的未成熟牦牛卵母细胞用不同浓度的雷帕霉素处理以选择最佳剂量。然后评估其对成熟率、卵裂和囊胚的影响形成率、线粒体膜电位、活性氧水平。还评估了成熟卵母细胞和胚泡中相关基因和蛋白质的表达。结果表明，IVM 期间 10 nM 雷帕霉素处理显着提高了卵母细胞的卵母细胞成熟率和囊胚形成率。用 10 nM 雷帕霉素处理降低了 ROS 水平，但增加了线粒体膜电位。相应地，成熟牦牛 COCs 中 LC3、Beclin-1 和 Bcl-2 的 mRNA 和蛋白质表达上调，而 Bax 下调。当孤雌胚胎用不同浓度的雷帕霉素处理时，10 nM 雷帕霉素处理显示出更高的 8 细胞和囊胚形成率。此外， CDX2、 POU5F1、SOX2和Nanog胚泡中的水平上调。总之，我们的研究结果表明，雷帕霉素治疗可能通过增加线粒体膜电位、降低 ROS 水平和调节成熟牦牛卵母细胞的凋亡来改善卵母细胞的成熟。雷帕霉素治疗还提高了牦牛的胚胎发育能力。