Department of Anatomy and Developmental Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia.
Reproduction. 2013 Oct 21;146(6):R205-15. doi: 10.1530/REP-13-0181. Print 2013 Dec.
The female germline comprises a reserve population of primordial (non-growing) follicles containing diplotene oocytes arrested in the first meiotic prophase. By convention, the reserve is established when all individual oocytes are enclosed by granulosa cells. This commonly occurs prior to or around birth, according to species. Histologically, the 'reserve' is the number of primordial follicles in the ovary at any given age and is ultimately depleted by degeneration and progression through folliculogenesis until exhausted. How and when the reserve reaches its peak number of follicles is determined by ovarian morphogenesis and germ cell dynamics involving i) oogonial proliferation and entry into meiosis producing an oversupply of oocytes and ii) large-scale germ cell death resulting in markedly reduced numbers surviving as the primordial follicle reserve. Our understanding of the processes maintaining the reserve comes primarily from genetically engineered mouse models, experimental activation or destruction of oocytes, and quantitative histological analysis. As the source of ovulated oocytes in postnatal life, the primordial follicle reserve requires regulation of i) its survival or maintenance, ii) suppression of development (dormancy), and iii) activation for growth and entry into folliculogenesis. The mechanisms influencing these alternate and complex inter-related phenomena remain to be fully elucidated. Drawing upon direct and indirect evidence, we discuss the controversial concept of postnatal oogenesis. This posits a rare population of oogonial stem cells that contribute new oocytes to partially compensate for the age-related decline in the primordial follicle reserve.
女性生殖细胞系包含一个原始（非生长）卵泡储备群体，其中包含处于第一次减数分裂前期的双线期卵母细胞。根据惯例，当所有的卵母细胞都被颗粒细胞包裹时，储备就建立起来了。这通常发生在出生前或出生时，具体取决于物种。从组织学上讲，“储备”是卵巢中任何特定年龄的原始卵泡数量，并且最终通过退化和通过卵泡发生进展耗尽，直到耗尽。储备达到其卵泡数量的峰值的方式和时间取决于涉及 i）卵原细胞增殖并进入减数分裂产生卵母细胞过剩和 ii）大量生殖细胞死亡导致作为原始卵泡储备存活的数量明显减少的卵巢形态发生和生殖细胞动力学。我们对维持储备的过程的理解主要来自于基因工程小鼠模型、卵母细胞的实验激活或破坏，以及定量组织学分析。作为出生后生活中排卵卵母细胞的来源，原始卵泡储备需要调节 i）其存活或维持、ii）抑制发育（休眠）和 iii）激活生长并进入卵泡发生。影响这些交替和复杂相互关联现象的机制仍有待充分阐明。根据直接和间接证据，我们讨论了产后发生卵子发生的有争议的概念。这假设了一小部分卵原干细胞的存在，它们为部分补偿原始卵泡储备与年龄相关的下降提供新的卵母细胞。
