Held Eva, Mertens Eva-Maria, Mohammadi-Sangcheshmeh Abdollah, Salilew-Wondim Dessie, Besenfelder Urban, Havlicek Vitezslav, Herrler Andreas, Tesfaye Dawit, Schellander Karl, Hölker Michael
Institute of Animal Science, Animal Breeding and Husbandry Group, University of Bonn, Endenicher Allee 15, 53115 Bonn, Germany.
Reprod Fertil Dev. 2012;24(4):568-79. doi: 10.1071/RD11112.
In the present study we aimed to analyse structural changes during in vitro maturation of the bovine zona pellucida (ZP) by scanning electron microscopy (SEM) ands zona pellucida birefringence (ZPB). Here we show that alterations during in vitro maturation invasively analysed by SEM are reflected in ZPB. In vivo-matured oocytes displayed significantly lower birefringence parameters and significantly higher blastocyst rates compared with in vitro-derived oocytes (39.1% vs 21.6%). The same was observed for in vitro-matured oocytes with cumulus-oocyte complex (COC) Quality 1 (Q1) compared with Q3-COCs with respect to zona birefringence and developmental capacity. Immature oocytes with Q1-COCs displayed higher ZPB values and a higher developmental capacity to the blastocyst stage (27.7% vs 16.9%) compared with immature Q3-COCs. Considering in vitro-matured oocytes, only those with Q1-COC showed a trend for ZPB similar to in vivo-matured oocytes. Therefore, a decreasing trend for ZPB during in vitro maturation seems to be typical for high-quality oocytes and successful cytoplasmic maturation. In accordance, fully-grown immature oocytes reached significantly higher blastocyst rates (32.0% vs 11.5%) and lower ZPB values compared with still-growing ones. In conclusion, we successfully evaluated the applicability of zona imaging to bovine oocytes: alterations during in vitro maturation invasively analysed by scanning electron microscopy were reflected in the birefringence of the zona pellucida of bovine oocytes affecting developmental capacity at the same value. Therefore ZPB measurement by live zona imaging has potential to become a new tool to assess correctness of in vitro maturation and to predict developmental competence.
在本研究中，我们旨在通过扫描电子显微镜（SEM）和透明带双折射（ZPB）分析牛透明带（ZP）体外成熟过程中的结构变化。在此我们表明，通过SEM进行侵入性分析的体外成熟过程中的变化反映在ZPB中。与体外来源的卵母细胞相比，体内成熟的卵母细胞显示出显著更低的双折射参数和显著更高的囊胚率（39.1%对21.6%）。在透明带双折射和发育能力方面，与质量为3（Q3）的卵丘-卵母细胞复合体（COC）相比，质量为1（Q1）的COC的体外成熟卵母细胞也观察到同样的情况。与未成熟的Q3-COC相比，具有Q1-COC的未成熟卵母细胞显示出更高的ZPB值和更高的发育至囊胚阶段的能力（27.7%对16.9%）。就体外成熟的卵母细胞而言，只有那些具有Q1-COC的卵母细胞显示出与体内成熟卵母细胞相似的ZPB趋势。因此，体外成熟过程中ZPB的下降趋势似乎是高质量卵母细胞和成功的细胞质成熟的典型特征。相应地，与仍在生长的未成熟卵母细胞相比，完全成熟的未成熟卵母细胞达到了显著更高的囊胚率（32.0%对11.5%）和更低的ZPB值。总之，我们成功评估了透明带成像对牛卵母细胞的适用性：通过扫描电子显微镜进行侵入性分析的体外成熟过程中的变化反映在牛卵母细胞透明带的双折射中，且在相同程度上影响发育能力。因此，通过实时透明带成像测量ZPB有潜力成为一种评估体外成熟正确性和预测发育能力的新工具。
