It has long been accepted that the complement of follicles within the ovary is formed before birth in humans, or shortly after birth in rodents, and that no follicles are formed thereafter. This follows entry of all oogonia into meiosis in fetal life, with no remaining germ stem cells in the ovary, in contrast to the presence of spermatogonia in the testis. This has been brought back into debate in recent years, following the demonstration of isolation of cells expressing both germline and stem markers from the postnatal ovary in several species, including humans. We describe these cells as putative ovarian stem cells. Isolation of these cells is challenging, adding to the debate as to their existence, and the validity of DDX4 as the main marker used for their isolation has also to be questioned. While different groups have used varying techniques and indeed terminology to describe these cells, the body of evidence regarding their initial characterization after isolation is growing. There remain very limited data regarding their developmental potential, but the demonstration of the production of functional oocytes from induced pluripotent stem cells and the advances in ovarian follicle culture techniques provide a basis for such studies.
长久以来我们都认为人体内的卵泡在出生前形成, 啮齿类的卵泡在出生后不久形成, 之后并不会增加。胎儿期所有卵原细胞进入有丝分裂后, 卵巢内没有剩余的生殖干细胞, 对比来讲, 而睾丸内则存在精原细胞。近年来, 随着从包括人类在内的一些物种在出生后的卵巢里分离出同时表达生殖系和干细胞标记的细胞, 这又引起了争论。我们把这些细胞假定为卵巢干细胞。分离这些细胞比讨论他们是否存在更有挑战性, DDX4----作为判断细胞是否被分离出的主要标志物, 也同样被质疑。虽然不同的研究小组使用了不同的技术和术语来描述这些细胞, 但有关分离后这些细胞最初特征的证据越来越多。关于多能干细胞发育潜能的资料非常有限, 但是从诱导多能干细胞中产生功能性卵母细胞的证据和卵巢卵泡培养技术的进展为此类研究提供了基础。
Keywords: Oogonial stem cells; neo-oogenesis; oocyte; ovarian regeneration.