The Department of Obstetrics and Gynecology, The Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
Mol Hum Reprod. 2009 Dec;15(12):795-803. doi: 10.1093/molehr/gap073. Epub 2009 Aug 26.
The creation of the pool of follicles available for selection and ovulation is a multi-faceted, tightly regulated process that spans the period from embryonic development through to the first reproductive cycle of the organism. In mice, this development can occur in mere weeks, but in humans, it is sustained for years. Embryonic germ cell development involves the migration of primordial germs cells to the genital ridge, and the mitotic division of germ cell nuclei without complete cytokinesis to form a multi-nucleated syncytia, or germ cell nest. Through combined actions of germ cell apoptosis and somatic cell migration, the germ cell nuclei are packaged, with surrounding granulosa cells, into primordial follicles to form the initial follicle pool. Though often dismissed as quiescent and possibly uninteresting, this initial follicle pool is actually quite dynamic. In a very strictly controlled mechanism, a large portion of the initial primordial follicles formed is lost by atresia before cycling even begins. Remaining follicles can undergo alternate fates of continued dormancy or selection leading to follicular growth and differentiation. Together, the processes involved in the fate decisions of atresia, sustained dormancy, or activation carve out the follicle pool of puberty, the pool of available oocytes from which all future reproductive cycles of the female can choose. The formation of the initial and pubertal follicle pools can be predictably affected by exogenous treatment with hormones or molecules such as activin, demonstrating the ways the ovary controls the quality and quantity of germ cells maintained. Here, we review the biological processes involved in the formation of the initial follicle pool and the follicle pool of puberty, address the alternate models for regulating germ cell number and outline how the ovary quality-controls the germ cells produced.
可供选择和排卵的卵泡池的形成是一个多方面的、严格调控的过程，跨越了从胚胎发育到生物体第一个生殖周期的整个过程。在小鼠中，这个过程可以在短短几周内发生，但在人类中，它持续了数年。胚胎生殖细胞的发育涉及原始生殖细胞向生殖嵴的迁移，以及生殖细胞核的有丝分裂分裂而不完全胞质分裂，形成多核合胞体或生殖细胞巢。通过生殖细胞凋亡和体细胞迁移的共同作用，生殖细胞核与周围的颗粒细胞一起被包装成原始卵泡，形成初始卵泡池。尽管原始卵泡池通常被认为是静止的，可能没有什么有趣之处，但实际上它非常活跃。在一个非常严格控制的机制中，大量形成的初始原始卵泡在开始循环之前就通过闭锁而丢失。剩余的卵泡可以通过继续休眠或选择导致卵泡生长和分化来经历不同的命运。闭锁、持续休眠或激活的命运决定过程共同塑造了青春期的卵泡池，即女性未来所有生殖周期都可以从中选择的可利用卵母细胞池。初始卵泡池和青春期卵泡池的形成可以通过外源激素或分子（如激活素）的处理来预测，这表明了卵巢控制维持的生殖细胞质量和数量的方式。在这里，我们回顾了形成初始卵泡池和青春期卵泡池的生物学过程，讨论了调节生殖细胞数量的替代模型，并概述了卵巢如何质量控制所产生的生殖细胞。
