Bui Thi Thu Hien, Belli Martina, Fassina Lorenzo, Vigone Giulia, Merico Valeria, Garagna Silvia, Zuccotti Maurizio
Laboratorio di Biologia dello Sviluppo, Dipartimento di Biologia e Biotecnologie "Lazzaro Spallanzani", University of Pavia, Pavia, Italy.
Dipartimento di Ingegneria Industriale e dell'Informazione, University of Pavia, Pavia, Italy.
Mol Reprod Dev. 2017 May;84(5):356-362. doi: 10.1002/mrd.22788. Epub 2017 Mar 14.
Full-grown mouse antral oocytes are classified as surrounding nucleolus (SN) or not-surrounding nucleolus (NSN), depending on the respective presence or absence of a ring of Hoechst-positive chromatin surrounding the nucleolus. In culture, both types of oocytes resume meiosis and reach the metaphase II (MII) stage, but following insemination, NSN oocytes arrest at the two-cell stage whereas SN oocytes may develop to term. By coupling time-lapse bright-field microscopy with image analysis based on particle image velocimetry, we provide the first systematic measure of the changes to the cytoplasmic movement velocity (CMV) occurring during the germinal vesicle-to-MII (GV-to-MII) transition of these two types of oocytes. Compared to SN oocytes, NSN oocytes display a delayed GV-to-MII transition, which can be mostly explained by retarded germinal vesicle break down and first polar body extrusion. SN and NSN oocytes also exhibit significantly different CMV profiles at four main time-lapse intervals, although this difference was not predictive of SN or NSN oocyte origin because of the high variability in CMV. When CMV profile was analyzed through a trained artificial neural network, however, each single SN or NSN oocyte was blindly identified with a probability of 92.2% and 88.7%, respectively. Thus, the CMV profile recorded during meiotic resumption may be exploited as a cytological signature for the non-invasive assessment of the oocyte developmental potential, and could be informative for the analysis of the GV-to-MII transition of oocytes of other species.
成熟的小鼠窦状卵泡卵母细胞根据核仁周围是否存在Hoechst阳性染色质环分为核仁周围型（SN）或非核仁周围型（NSN）。在培养过程中，两种类型的卵母细胞都能恢复减数分裂并达到中期II（MII）阶段，但受精后，NSN卵母细胞会停滞在二细胞阶段，而SN卵母细胞则可能发育至足月。通过将延时明场显微镜与基于粒子图像测速技术的图像分析相结合，我们首次系统地测量了这两种类型的卵母细胞在生发泡至MII（GV至MII）转变过程中细胞质运动速度（CMV）的变化。与SN卵母细胞相比，NSN卵母细胞的GV至MII转变延迟，这主要可以通过生发泡破裂和第一极体排出延迟来解释。SN和NSN卵母细胞在四个主要的延时时间间隔也表现出显著不同的CMV特征，尽管由于CMV的高度变异性，这种差异并不能预测SN或NSN卵母细胞的来源。然而，当通过训练有素的人工神经网络分析CMV特征时，每个单独的SN或NSN卵母细胞被正确识别的概率分别为92.2%和88.7%。因此，减数分裂恢复过程中记录的CMV特征可作为一种细胞学特征，用于非侵入性评估卵母细胞的发育潜力，并且可能为分析其他物种卵母细胞的GV至MII转变提供信息。
