Vincent Center for Reproductive Biology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
Semin Reprod Med. 2013 Jan;31(1):24-32. doi: 10.1055/s-0032-1331794. Epub 2013 Jan 17.
The concept that oogenesis continues into reproductive life has been well established in nonmammalian species. Recent studies of mice and women indicate that oocyte formation is also not, as traditionally believed, restricted to the fetal or perinatal periods. Analogous to de novo oocyte formation in flies and fish, newly formed oocytes in adult mammalian ovaries arise from germline stem cells (GSCs) or, more specifically, oogonial stem cells (OSCs). Studies of mice have confirmed that isolated OSCs, once delivered back into adult ovaries, are capable of generating fully functional eggs that fertilize to produce healthy embryos and offspring. Parallel studies of OSCs recently purified from ovaries of reproductive-age women indicate that these cells closely resemble their mouse ovary-derived counterparts, although the fertilization competency of oocytes generated by human OSCs awaits clarification. Despite the ability of OSCs to produce new oocytes during adulthood, oogenesis will still ultimately cease with age, contributing to ovarian failure. The causal mechanisms behind these events in mammals are unknown, but studies of flies have revealed that GSC niche dysfunction plays a critical role in age-related oogenic failure. Such insights derived from evaluation of nonmammalian species, in which postnatal oogenesis has been studied in depth, may aid in development of new strategies to alleviate ovarian failure and infertility in mammals.
卵母细胞发生持续到生殖期的概念在非哺乳动物物种中已经得到很好的确立。最近对小鼠和女性的研究表明，卵母细胞的形成也不像传统上认为的那样仅限于胎儿期或围产期。与果蝇和鱼类中的新卵母细胞形成类似，成年哺乳动物卵巢中的新形成的卵母细胞来自生殖干细胞（GSCs），或者更具体地说，来自卵原干细胞（OSCs）。对小鼠的研究证实，分离的 OSCs 一旦被送回成年卵巢，就能够产生完全功能的卵子，这些卵子能够受精产生健康的胚胎和后代。最近对从育龄女性卵巢中纯化的 OSCs 的平行研究表明，这些细胞与它们的小鼠卵巢来源的对应物非常相似，尽管人类 OSCs 产生的卵子的受精能力仍有待澄清。尽管 OSCs 在成年期能够产生新的卵母细胞，但卵母细胞发生最终仍会随着年龄的增长而停止，导致卵巢衰竭。哺乳动物中这些事件背后的因果机制尚不清楚，但对果蝇的研究表明，GSC 生态位功能障碍在与年龄相关的卵母细胞发生失败中起着关键作用。从对深入研究了产后卵母细胞发生的非哺乳动物物种的评估中得出的这些见解，可能有助于开发新的策略来缓解哺乳动物的卵巢衰竭和不孕。
