Wortzman Genevieve B, Evans Janice P
Department of Biochemistry and Molecular Biology, Division of Reproductive Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA.
Mol Hum Reprod. 2005 Jan;11(1):1-9. doi: 10.1093/molehr/gah125. Epub 2004 Oct 29.
Fertilization at increased times after ovulation is associated with poor reproductive outcomes. This study examines the effects of post-ovulatory ageing on egg membrane function through analyses of mouse eggs collected at 13 and 22 h post-HCG ('young' and 'aged' eggs, respectively). Experiments in which fertilized zona pellucida-free young and aged eggs are challenged with additional sperm reveal that aged eggs are less able to establish a membrane block to prevent polyspermy, since sperm penetrate 24% of fertilized aged eggs but are unable to penetrate fertilized young eggs. This is not due to a failure of aged eggs to respond to fertilization, as the extent of sperm-induced cortical granule exocytosis is similar in aged and young eggs. Post-ovulatory ageing also affects egg membrane receptivity to sperm as a subset of zona pellucida-free aged eggs are slow to fertilize or resistant to fertilization. Sperm binding to young and aged eggs is similar, but aged eggs develop cytoskeletal abnormalities that may affect membrane/cortical function, such as the ability of the egg membrane to support sperm-egg fusion. These data demonstrate that the poor reproductive outcomes associated with post-ovulatory ageing could be a result of reduced fertilization, due to reduced egg membrane receptivity to sperm, or a result of increased incidence of polyspermy, due to the reduced ability to establish a membrane block to polyspermy. This analysis of egg membrane function deficiencies provides insights into post-ovulatory ageing and has implications for assisted reproductive technologies.
排卵后延长受精时间与不良生殖结局相关。本研究通过分析在注射人绒毛膜促性腺激素（HCG）后13小时和22小时收集的小鼠卵子（分别为“年轻”卵子和“老化”卵子），研究排卵后卵子老化对卵膜功能的影响。对去除透明带的年轻和老化受精卵子用额外精子进行刺激的实验表明，老化卵子建立防止多精受精的膜阻断能力较弱，因为精子可穿透24%的老化受精卵子，但无法穿透年轻受精卵子。这并非由于老化卵子对受精无反应，因为老化卵子和年轻卵子中精子诱导的皮质颗粒胞吐程度相似。排卵后卵子老化还会影响卵膜对精子的接受能力，因为一部分去除透明带的老化卵子受精缓慢或对受精有抗性。精子与年轻卵子和老化卵子的结合情况相似，但老化卵子会出现细胞骨架异常，这可能会影响膜/皮质功能，例如卵膜支持精卵融合的能力。这些数据表明，与排卵后卵子老化相关的不良生殖结局可能是由于卵膜对精子的接受能力降低导致受精减少的结果，或者是由于建立多精受精膜阻断能力降低导致多精受精发生率增加的结果。对卵膜功能缺陷的分析为排卵后卵子老化提供了见解，并对辅助生殖技术具有启示意义。
