Lenie Sandy, Cortvrindt Rita, Eichenlaub-Ritter Ursula, Smitz Johan
Follicle Biology Laboratory, Vrije Universiteit Brussel, Laarbeeklaan 101, B-1090 Brussels, Belgium.
Mutat Res. 2008 Mar 12;651(1-2):71-81. doi: 10.1016/j.mrgentox.2007.10.017. Epub 2007 Nov 12.
Bisphenol A (BPA), a widely used environmental contaminant, may exert weak estrogenic, anti-androgenic and anti-thyroidic activities. BPA is suspected to possess aneugenic properties that may affect somatic cells and mammalian oocytes. Oocyte growth and maturation depend upon a complex bi-directional signaling between the oocyte and its companion somatic cells. Consequently, disturbances in oocyte maturation may originate either from direct effects of BPA at the level of the oocyte or from indirect influences at the follicular level, such as alterations in hormonal homeostasis. This study aimed to analyze the effects of chronic BPA exposure (3 nM to 30 microM) on follicle-enclosed growth and maturation of mouse oocytes in vitro. Oocytes were cultured and their spindle and chromosomes were stained by alpha-tubulin immunofluorescence and ethidium homodimer-2, respectively. Confocal microscopy was utilized for subsequent analysis. Only follicles that were exposed to 30 microM BPA during follicular development showed a slightly reduced granulosa cell proliferation and a lower total estrogen production, but they still developed and formed antral-like cavities. However, 18% of oocytes were unable to resume meiosis after stimulation of oocyte maturation, and 37% arrested after germinal vesicle breakdown, significantly different from controls (p<0.05). Only 45% of the oocytes extruded a first polar body (p < 0.05). 30 microM BPA led also to a significant increase in meiosis I-arrested oocytes with unaligned chromosomes and spindle aberrations. Oocytes that were able to progress beyond meiosis I, frequently arrested at an abnormal telophase I. Additionally, in many oocytes exposed to low chronic BPA that matured to meiosis II chromosomes failed to congress at the spindle equator. In conclusion, mouse follicle culture reveals non-linear dose-dependent effects of BPA on the meiotic spindle in mouse oocytes when exposure was chronic throughout oocyte growth and maturation.
双酚A（BPA）是一种广泛使用的环境污染物，可能具有微弱的雌激素活性、抗雄激素活性和抗甲状腺活性。有人怀疑双酚A具有非整倍体诱导特性，可能会影响体细胞和哺乳动物卵母细胞。卵母细胞的生长和成熟取决于卵母细胞与其相伴体细胞之间复杂的双向信号传导。因此，卵母细胞成熟的紊乱可能源于双酚A在卵母细胞水平的直接作用，也可能源于卵泡水平的间接影响，如激素稳态的改变。本研究旨在分析慢性暴露于双酚A（3 nM至30 μM）对体外培养的小鼠卵泡包被卵母细胞生长和成熟的影响。对卵母细胞进行培养，并用α-微管蛋白免疫荧光和乙锭同二聚体-2分别对其纺锤体和染色体进行染色。随后利用共聚焦显微镜进行分析。只有在卵泡发育过程中暴露于30 μM双酚A的卵泡显示颗粒细胞增殖略有减少，总雌激素产量较低，但它们仍能发育并形成类似腔卵泡的腔。然而，18%的卵母细胞在卵母细胞成熟刺激后无法恢复减数分裂，37%在生发泡破裂后停滞，与对照组有显著差异（p<0.05）。只有45%的卵母细胞排出了第一极体（p<0.05）。30 μM双酚A还导致减数分裂I停滞的卵母细胞中染色体排列不齐和纺锤体畸变显著增加。能够进入减数分裂I后期的卵母细胞，经常在异常的末期I停滞。此外，在许多暴露于低剂量慢性双酚A并成熟至减数分裂II的卵母细胞中，染色体未能在纺锤体赤道处排列。总之，小鼠卵泡培养显示，在卵母细胞整个生长和成熟过程中进行慢性暴露时，双酚A对小鼠卵母细胞减数分裂纺锤体具有非线性剂量依赖性影响。
