Higaki Shogo, Kishi Masao, Koyama Keisuke, Nagano Masashi, Katagiri Seiji, Takada Tatsuyuki, Takahashi Yoshiyuki
Laboratory of Cell Engineering,Department of Pharmaceutical Sciences,Ritsumeikan University,Nojihigashi 1-1-1,Kusatsu,Shiga 525 8577,Japan.
Laboratory of Theriogenology,Department of Veterinary Clinical Sciences,Graduate School of Veterinary Medicine,Hokkaido University,Sapporo,Hokkaido 060-0818,Japan.
Zygote. 2017 Feb;25(1):41-48. doi: 10.1017/S0967199416000290. Epub 2016 Nov 22.
The preselection of highly developmentally competent oocytes for in vitro maturation (IVM) is crucial for improving assisted reproductive technology. Although several intrinsic markers of oocyte quality are known to be closely related to the onset of nuclear maturation (germinal vesicle break down, GVBD), a direct comparison between GVBD timing and oocyte quality has never been reported. In this study, we established a non-invasive oocyte evaluation method based on GVBD timing for preselecting more developmental competent oocytes in mice. Because the O2 concentration during IVM may affect the nuclear kinetics, all experiments were performed under two distinct O2 concentrations: 20% and 5% O2. First, we determined the time course of changes in nuclear maturation and preimplantation developmental competence of in vitro-matured oocytes to estimate GVBD timing in high developmental competent oocytes. Two-thirds of oocytes that underwent GVBD in early IVM seemed to mainly contribute to the blastocyst yield. To confirm this result, we compared the preimplantation developmental competence of the early and late GVBD oocytes. Cleavage and blastocyst formation rates of early GVBD oocytes (80.2% and 52.7% under 20% O2, respectively, and 67.6% and 47.3% under 5% O2, respectively) were almost double those of late GVBD oocytes (44.8% and 26.0% under 20% O2, respectively, and 40.4% and 17.9% under 5% O2, respectively). With no observable alterations by checking the timing of GVBD in preimplantation developmental competence, oocyte evaluation based on GVBD timing can be used as an efficient and non-invasive preselection method for high developmental competent oocytes.
为提高辅助生殖技术，预先选择发育潜能高的卵母细胞进行体外成熟（IVM）至关重要。尽管已知几种卵母细胞质量的内在标志物与核成熟的开始（生发泡破裂，GVBD）密切相关，但GVBD时间与卵母细胞质量之间的直接比较从未见报道。在本研究中，我们基于GVBD时间建立了一种非侵入性卵母细胞评估方法，用于在小鼠中预先选择更多具有发育潜能的卵母细胞。由于IVM期间的O2浓度可能影响核动力学，所有实验均在两种不同的O2浓度下进行：20%和5% O2。首先，我们确定了体外成熟卵母细胞核成熟和植入前发育潜能的时间变化过程，以估计高发育潜能卵母细胞的GVBD时间。在IVM早期发生GVBD的卵母细胞中有三分之二似乎主要促成了囊胚的产出。为证实这一结果，我们比较了早期和晚期GVBD卵母细胞的植入前发育潜能。早期GVBD卵母细胞的卵裂率和囊胚形成率（在20% O2下分别为80.2%和52.7%，在5% O2下分别为67.6%和47.3%）几乎是晚期GVBD卵母细胞（在20% O²下分别为44.8%和26.0%，在5% O2下分别为40.4%和17.9%）的两倍。通过检查GVBD时间在植入前发育潜能方面未观察到明显变化，基于GVBD时间的卵母细胞评估可作为一种高效且非侵入性的高发育潜能卵母细胞预选方法。
