Characterization of the TGF-beta receptor system in bovine granulosa cells

奶牛不孕不育是制约奶牛业经济成功的主要因素。毛囊生长和发情异常是高产奶牛生育力下降的主要原因之一。要解决这个问题，需要更多的基础知识来了解控制卵泡生长的内分泌机制，卵泡是包含卵母细胞的结构。卵泡壁颗粒细胞产生雌二醇是确保卵泡正常发育的关键，而雌二醇的分泌涉及循环分子和局部产生的因子之间复杂的相互作用。转化生长因子是一种由卵泡细胞产生的重要因子，可调节雌二醇的分泌、卵巢功能和生育能力。在我们先前和正在进行的研究中，我们已经证明转化生长因子-1是一种多功能因子，它抑制FSH刺激的雌二醇的分泌，但在基础条件下(即在没有FSH的情况下)刺激雌二醇的分泌。我的研究计划的总体目标是确定转化生长因子对牛颗粒细胞雌二醇分泌的作用机制。培养的牛颗粒细胞将被用来表征转化生长因子配体/受体系统。第一个目标是研究关键激素(卵泡刺激素、雄烯二酮、胰岛素样生长因子和胰岛素)对转化生长因子受体(ALK-5、转化生长因子受体II和β-聚糖)mRNA表达的影响。第二个目标是利用牛基因芯片研究1)转化生长因子-β亚型对Smads基因表达和激活的影响以及2)转化生长因子-β1在基础和促卵泡激素刺激条件下对基因表达的差异影响，以确定转化生长因子-β受体的信号转导机制。第三个目标是研究不同大小的牛卵泡中转化生长因子受体系统的特征。本研究计划中对牛卵泡中转化生长因子受体/配体系统的研究将为进一步研究营养和胁迫对雌二醇分泌和卵泡发育的影响以提高牛的繁殖力奠定基础。

Infertility in dairy cattle is a principal restraint on economic success in the industry. Abnormal follicle growth and anoestrus is one of the principal causes in declining fertility in high-yielding dairy cattle. To resolve this problem, more basic knowledge is required to understand the endocrine mechanisms that control growth of the ovarian follicle which is the structure that contains the oocyte. Estradiol production by the granulosa cells of the follicle wall is the key to ensure normal follicle development, and estradiol secretion involves complex interactions between circulating molecules and locally produced factors. Transforming growth factor-ß (TGF-ß) is an important factor produced by the follicle cells and is known to modulate estradiol secretion, ovarian function and fertility. In our previous and ongoing studies we have shown that TGF-ß1 is a multifunctional factor which inhibits FSH-stimulated estradiol secretion but stimulates the secretion of estradiol in basal conditions (i.e. in the absence of FSH). The overall objective of my research program is to determine the mechanism of action of TGF-ß on estradiol secretion in bovine granulosa cells. Cultured bovine granulosa cells will be used to characterize the TGF-ß ligand/receptor system. The first objective is to characterize the effects of key hormones (FSH, androstenedione, IGF and insulin) on the mRNA expression of TGF-ß receptors (ALK-5, TGF-ßRII and betaglycan). The second objective is to determine the signal transduction mechanism of TGF-ß receptors looking at 1) the effects of TGF-ß isoforms on the mRNA expression and activation of Smads and 2) the differential effects of TGF-ß1 on gene expression in both basal and FSH-stimulated conditions using bovine gene microarrays. The third objective is to characterize the receptor system of TGF-ß in bovine follicles of different sizes. The study of the TGF-ß receptor/ligand system in bovine follicles as proposed in this research program will provide the basis for future research examining the effects of nutrition and stress on estradiol secretion and follicle development to improve fertility in the bovine species.