Fortune J E, Kito S, Byrd D D
Department of Physiology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
J Reprod Fertil Suppl. 1999;54:439-48.
The resting pool of primordial follicles in mammalian ovaries is a potential resource for the genetic manipulation of domestic animals, the preservation of endangered species, and the amelioration of some forms of infertility in humans. Exploitation of this large reservoir of follicles depends on the development of methods for activating primordial follicles to begin growth in vitro and of methods for sustaining follicular growth to the stage at which oocytes are capable of meiotic maturation, fertilization and development to live young. It has been shown that primordial follicles of rodents, cattle and primates can initiate growth in vitro, even in serum-free medium. The signals that cause primordial follicles to leave the resting pool or remain quiescent are unknown. However, of interest is the observation that in cultures of whole rodent ovaries an apparently normal number of follicles leaves the resting pool and begins to grow, whereas in cultures of isolated bovine or primate ovarian cortex almost all primordial follicles activate and develop into primary follicles. This finding suggests that non-cortical portions of the ovary may regulate the flow of follicles from the resting reservoir. In cattle, it has been difficult to sustain follicular growth beyond the primary stage and the development of methods for doing so are critical for achievement of the practical goal of use of the primordial pool for embryo production. However, the development of murine follicles in vitro from the primordial stage through oocyte maturation and fertilization, and the birth of one pup, provides encouragement for efforts to achieve similar results in large mammals.
哺乳动物卵巢中原始卵泡的静止库是家畜基因操作、濒危物种保护以及改善人类某些形式不孕症的潜在资源。对这个庞大卵泡库的开发依赖于激活原始卵泡在体外开始生长的方法以及将卵泡生长维持到卵母细胞能够进行减数分裂成熟、受精并发育成活体幼崽阶段的方法的开发。已经表明，啮齿动物、牛和灵长类动物的原始卵泡即使在无血清培养基中也能在体外启动生长。导致原始卵泡离开静止库或保持静止的信号尚不清楚。然而，有趣的是观察到，在整个啮齿动物卵巢培养物中，有明显正常数量的卵泡离开静止库并开始生长，而在分离的牛或灵长类动物卵巢皮质培养物中，几乎所有原始卵泡都会激活并发育成初级卵泡。这一发现表明卵巢的非皮质部分可能调节卵泡从静止库中的流出。在牛中，很难将卵泡生长维持到初级阶段之后，而开发这样做的方法对于实现利用原始卵泡库进行胚胎生产这一实际目标至关重要。然而，小鼠卵泡在体外从原始阶段发育到卵母细胞成熟、受精并产下一只幼崽，这为在大型哺乳动物中取得类似结果的努力提供了鼓舞。
