Role of thecal inhibin alpha subunit in the regulation of INSL3-dependent androgen production in the ovary

雌性动物和人类的生育力需要从卵巢中正确定时释放一个或多个健康的卵子（卵母细胞）。卵子在一种叫做卵泡的结构中发育，卵泡也能合成重要的激素，没有这些激素，生殖就会失败。这项研究将研究这些激素的产生是如何调节的。特别是，两种相关的激素称为雄激素和雌激素，必须由专门的卵泡细胞以正确的数量产生，并在女性周期的正确时间。雄激素由卵泡膜细胞（TC）产生，而雌激素由颗粒细胞（GC）产生。GC只有在邻近TC提供雄激素时才能合成雌激素。卵泡从微观结构生长成大的多层结构，直径约2厘米（人类和牛）。来自垂体的促黄体激素（LH）脉冲刺激TC产生雄激素，而促卵泡激素（FSH）刺激GC增殖并将雄激素转化为雌激素。成熟的卵泡从卵巢表面突出，等待来自垂体的激素触发（LH激增），使它们排卵并释放卵子以进行可能的受精。反过来，这种LH激增取决于生长中的卵泡分泌越来越多的雌激素。在动物中，这种雌激素的增加也会引发重要的行为变化（“热”），没有这种变化，交配就不会发生。雌激素在准备怀孕的生殖道中也起着关键作用，雄激素和雌激素都会影响身体周围的许多其他组织和器官。因此，卵泡发育障碍导致TC产生雄激素或GC产生雌激素的失衡不仅会导致不孕，而且会影响许多其他生理方面。例如，多囊卵巢综合征（PCOS）是一种非常常见的女性不孕症/生育力低下的原因，它与卵巢雄激素分泌过多有关;这种情况会导致月经周期紊乱以及面部和身体毛发的过度生长。卵泡发育是一个复杂的过程，目前仍知之甚少。现在很清楚，卵巢本身产生了许多信号分子，使不同的细胞类型能够相互交流。这种“局部”细胞间的通讯与来自垂体的激素信号（LH，FSH）协同作用，以协调卵泡生长和类固醇产生。在这个项目中，我们将扩展我们以前的BBSRC资助的研究结果，重点是两个不同的“本地”信号系统在调节卵巢雄激素的产生-INSL 3系统和BMP系统的行动和相互作用。特别是，我们将研究另一种分子的功能作用，我们最近发现，TC产生了惊人的大量，称为tubin α亚基。虽然这种分子在TC中的作用目前尚不清楚，但我们预测其“局部”功能是“保护”TC免受来自卵泡中邻近GC的Escherichin的刺激。这可能是一个非常重要的作用，因为我们以前已经表明，BMPs可以拮抗对TC雄激素产生的抑制作用。BMP反过来又抑制INSL 3的TC表达，这似乎是TC雄激素产生的关键要求。我们预测，在卵泡发育过程中，上述信号之间的相对“平衡”会发生变化，我们将通过实验对此进行研究。此外，我们还将研究奶牛TC、卵泡液和外周血样本中的α-谷氨酰胺结合素α亚基水平之间的关系。通过分析先前研究中采集的奶牛血液样本，我们还将检验我们的预测，即循环INSL 3和雄激素水平在免疫牛中升高。总的来说，这些研究将大大促进对卵巢生理学的理解，并为不孕症的主要原因提供见解。

Fertility of female animals and humans requires the correctly-timed release of one or more healthy eggs (oocytes) from the ovaries. Eggs develop within structures called ovarian follicles that also synthesise important hormones, without which reproduction would fail. This research will investigate how the production of these hormones is regulated. In particular, two related hormones called androgen and oestrogen must be produced by specialized follicle cells in the right amounts, and at the right time of the female cycle. Androgen is produced by cells called theca cells (TC) whilst oestrogen is produced by granulosa cells (GC). GC can only synthesize oestrogen when supplied with androgen by neighbouring TC. Follicles grow from microscopic structures into large multi-layered structures ~ 2cm across (in human & cow). Pulses of luteinizing hormone (LH) from the pituitary stimulate TC to produce androgen while follicle-stimulating hormone (FSH) stimulates GC to proliferate and convert androgen into oestrogen. Mature follicles protrude from the ovary surface awaiting a hormonal trigger from the pituitary (LH surge) that causes them to ovulate and release the egg(s) for possible fertilization. This LH surge, in turn, depends on the secretion of increasing amounts of oestrogen by the growing follicle. In animals, this oestrogen rise also triggers vital behavioural changes ('heat') without which mating would not occur. Oestrogen also plays a key role in preparing the reproductive tract for pregnancy and both androgen and oestrogen affect many other tissues and organs around the body. Thus, disordered follicle development leading to an imbalance in production of androgen by TC or of oestrogen by GC can not only cause infertility, but can affect many other aspects of physiology. For instance, a very common cause of infertility/subfertility in women called polycystic ovarian disease syndrome (PCOS) is associated with excess ovarian androgen production; this condition leads to disturbed menstrual cycles and excess growth of facial and body hair.Follicle development is an intricate process that is still poorly understood. It is now clear that numerous signaling molecules are produced within the ovary itself that enable different cell-types to communicate with each other. This 'local' cell-cell communication works in concert with hormonal signals from the pituitary (LH, FSH) to coordinate follicle growth and steroid production. In this project we will extend the findings of our previous BBSRC-funded grant that focused on the actions and interactions of two different 'local' signaling systems in regulating ovarian androgen production - the INSL3 system and the BMP system. In particular, we will investigate the functional role of another molecule called inhibin alpha subunit that we recently found to be produced in surprisingly large amounts by TC. While the role of this molecule in TC is currently unknown, we predict that its 'local' function is to 'protect' TC from stimulation by inhibin from neighbouring GC in the follicle. This is potentially a very important role since we have previously shown that inhibin can antagonise the suppressive action of BMPs on TC androgen production. BMPs, in turn, suppress TC expression of INSL3 that seems to be a critical requirement for TC androgen production. We predict that the relative 'balance' between the above signals varies during the course of follicle development and we will examine this experimentally. In addition, we will investigate the relationship between inhibin alpha subunit levels in TC, follicular fluid and peripheral blood samples from cows. By analysing cow blood samples collected for a previous study we will also test our prediction that circulating INSL3 and androgen levels are raised in cows immunized against inhibin alpha subunit. Collectively, these studies will significantly advance understanding of ovarian physiology and provide insights into a major cause of infertility.