Aging and Ovarian Stem Cell Niche Dysfunction

描述（由申请人提供）：干细胞生物学中最令人兴奋的领域之一涉及干细胞功能障碍在与衰老相关的器官功能恶化中发挥核心作用的可能性。近年来的研究表明，在成年哺乳动物卵巢中存在产卵干细胞（ocs）。OSCs的存在增加了卵巢衰老的可能性，其特征是含有卵母细胞的卵泡的丢失和耗尽，同样可能涉及干细胞功能的逐渐丧失。因此，确定OSCs在卵巢功能和衰老中的生理作用是非常重要的。我的长期目标是确定衰老过程如何对OSC功能产生负面影响，从而使用OSC作为模型来深入了解基于干细胞的机体衰老机制。具体来说，我建议使用我们在过去三年中开发的新型自杀基因转基因（sg-Tg）小鼠模型来研究这一点。这些小鼠模型的独特之处在于，分化的OSC子细胞可以选择性地靶向并使用自杀基因技术进行消融。在我们的初步数据中，我们表明选择性破坏这些OSC分化途径导致遗传上定义的可逆原始卵泡损失。这些发现支持了哺乳动物卵巢中卵母细胞储备在成年期的维持与来自osc的新卵母细胞的主动输入有关。这些数据也为未来卵巢生物学和疾病发病机制的研究奠定了坚实的基础，提供了前所未有的可能性，包括了解女性生殖衰老，OSC对卵巢功能的贡献。本提案的具体目的是：1)利用我们开发的新型sg-Tg小鼠，可以选择性地消融分化的OSC子细胞，建立OSC在卵巢衰老中的生理作用；2)分别评价胶质细胞源性神经营养因子（GDNF）和成纤维细胞生长因子（FGF9）作为刺激OSC增殖和抑制OSC减数分裂分化可能的生态位因子；3)研究海盐细胞有丝分裂活性升高期间海盐细胞生态位的特征，并研究血管内皮细胞在生态位功能中的作用；4)利用卵巢体细胞作为饲养细胞，改善OSC培养条件，在体外总结OSC与生态位的相互作用，并研究衰老对OSC活性的影响。最终，这些信息可能用于开发新的靶向治疗方法，通过刺激OSC活性来增加卵母细胞储备，从而在需要时挽救卵巢功能，例如卵巢早衰患者。在高龄产妇（推迟与年龄相关的卵巢功能衰竭和更年期）或女性癌症患者（在抗癌治疗后挽救其卵巢功能和生育能力）中，所有这些情况都显示出越来越多的公共卫生相关性。

DESCRIPTION (provided by applicant): One of the most exciting areas of stem cell biology relates to the possibility that stem cell dysfunction plays central role in aging-related deterioration of organ function. Recent studies suggest that oogonial (oocyte- producing) stem cells (OSCs) exist in the adult mammalian ovary. Existence of OSCs raises the possibility that ovarian aging, marked by loss and exhaustion of oocyte-containing follicles, may similarly involve a progressive loss of stem cell function. Thus, it is now important to establish the physiological roles of OSCs in ovarian function and aging. My long-term goal is to determine how the aging process negatively affects OSC function, and thus use OSCs as a model to provide insight into stem cell-based mechanisms for organismal aging. Specifically, I propose to use novel suicide gene transgenic (sg-Tg) mouse models we have developed over the past three years to study this. These mouse models are unique in that differentiating OSC daughter cells can be selectively targeted and ablated using suicide gene technology. In our preliminary data, we show that selective disruption of these OSC differentiation pathways results in a genetically defined reversible loss of primordial follicles. These findings support that the maintenance of the oocyte reserve in mammalian ovaries during adulthood involves active input of new oocytes from OSCs. These data also lay a solid foundation for future studies of ovarian biology and disease pathogenesis with unprecedented possibilities, including an understanding of female reproductive aging that accounts for OSC contribution to ovarian function. The specific aims of this proposal are to: 1) establish the physiological roles of OSCs in ovarian aging using novel sg-Tg mice we have developed, in which differentiating OSC daughter cells can be selectively ablated; 2) evaluate glial cell-derived neurotrophic factor (GDNF) and fibroblast growth factor (FGF9) as possible OSC niche factors in stimulating OSC proliferation and suppressing OSC meiotic differentiation, respectively; 3) characterize OSC niches during periods of increased OSC mitotic activity and examine the participation of vascular endothelial cells in niche function; and, 4) develop improved OSC culture conditions by using ovarian somatic cells as feeder cells to recapitulate OSC-niche interaction ex vivo and examine the impact of aging on OSC activity. Ultimately, this information might be used to develop novel and targeted therapeutics that rescue ovarian function through increasing the oocyte reserve by stimulating OSC activity when it would be desirable - such as in patients with premature ovarian failure, in women of advanced maternal age (to postpone age- related ovarian failure and menopause) or in female cancer patients (to rescue their ovarian function and fertility after anti-cancer treatments) - all of these conditions represent increasing public health relevance. PUBLIC HEALTH RELEVANCE: Ovarian aging is an inevitable process that affects every woman. Maintenance of ovarian function in aging females might provide a means to achieve significant improvements in health, well-being and life expectancy. Thus, with efforts to continue to extend life span, the question of how to delay or even reverse the deleterious effect of ovarian aging has gained increasing public health relevance.