Mechanisms Affecting Oocyte Competence in the Bovine Model: EFFECT OF FOLLICULAR AND MATERNAL AGING

影响妊娠成败的最关键时期是胚胎发育的前7天。超过95%的卵母细胞（卵子）在受精（受孕）后受精，但超过50%的胚胎无法发育。这种高失败率的原因尚不清楚，但与卵母细胞及其生长的卵泡的质量有关（卵泡是由颗粒细胞和卵泡膜细胞组成的充满液体的结构）。我的研究计划的长期目标是阐明影响卵母细胞发育成健康胚胎的能力的内分泌、细胞和分子机制（即，卵母细胞能力）。本文提出的研究是基于2002年建立的一个富有成效的研究路线，并与以前的NSERC资金成为可能。我在萨斯喀彻温大学的研究小组已经开发了用于研究生殖衰老的牛模型，并证明母亲的年龄（母亲衰老）与卵母细胞能力的下降有关。我们还发现，当生长卵泡的寿命延长3-4天（卵泡老化）时，卵母细胞的能力会受到损害。我们建议解决基本的生物学问题：卵母细胞功能障碍是如何发生的，哪些分子途径负责卵泡和母体衰老的影响？我们的工作假设是卵母细胞能力的丧失是由母体和卵泡衰老过程中相似的细胞变化引起的。本研究的具体目标是确定1）在排卵卵泡的颗粒细胞中的精确分子途径，这些分子途径在母体和卵泡老化期间上调或下调，2）卵泡膜细胞在卵母细胞能力丧失中的作用，以及3）老化卵母细胞中的哪些特定基因和分子途径负责发育失败。从这些研究中获得的信息对衰老生物学具有广泛的影响，并与动物和人类有效辅助生殖技术的发展密切相关。我们预计，我们的研究结果将允许直接改进牛的人工授精，超数排卵和体外胚胎生产技术。

The most critical period influencing the success or failure of pregnancy is the first 7 days of embryo development. More than 95% of oocytes (eggs) become fertilized after insemination (conception) but >50% embryos fail to develop. The reason for this high rate of failure is unclear, but is associated with quality of the oocyte and the ovarian follicle in which it grows (follicle is a fluid-filled structure composed of granulosa and theca cells). The long-term objective of my research program is to elucidate the endocrine, cellular and molecular mechanisms that affect an oocyte's ability to develop into a healthy embryo (i.e., oocyte competence). Studies proposed herein are based on a fruitful line of research established in 2002 and made possible with previous NSERC funding. My research team at the University of Saskatchewan has developed the bovine model for the study of reproductive aging and documented that mother's age (maternal aging) is associated with a decrease in oocyte competence. We have also discovered that oocyte competence is compromised when the life-span of a growing follicle is prolonged by as little as 3-4 days (follicular aging). We propose to address the fundamental biological question: How does oocyte dysfunction occur and which molecular pathways are responsible for the effects of follicular and maternal aging? Our working hypothesis is that the loss of oocyte competence is caused by similar cellular changes during maternal and follicular aging. The specific objectives of this research are to determine 1) the precise molecular pathways in the granulosa cells of the ovulatory follicle that are either up- or down-regulated during maternal and follicular aging, 2) the role of theca cells in loss of oocyte competence, and 3) which specific genes and molecular pathways in the aged oocyte are responsible for the developmental failure. Information gained from these studies has broad implications regarding the biology of aging and is germane to the development of efficient assisted reproductive techniques for animals and humans. We anticipate that our results will allow direct improvements of artificial insemination, superovulation and in vitro embryo production techniques in cattle.