Human germ cells perpetuate human genetic and epigenetic information. However, the underlying mechanism remains elusive, due to a lack of appropriate experimental systems. Here, we show that human primordial germ cell‐like cells (hPGCLCs) derived from human‐induced pluripotent stem cells (hiPSCs) can be propagated to at least ~10⁶‐fold over a period of 4 months under a defined condition in vitro. During expansion, hPGCLCs maintain an early hPGC‐like transcriptome and preserve their genome‐wide DNA methylation profiles, most likely due to retention of maintenance DNA methyltransferase activity. These characteristics contrast starkly with those of mouse PGCLCs, which, under an analogous condition, show a limited propagation (up to ~50‐fold) and persist only around 1 week, yet undergo cell‐autonomous genome‐wide DNA demethylation. Importantly, upon aggregation culture with mouse embryonic ovarian somatic cells in xenogeneic‐reconstituted ovaries, expanded hPGCLCs initiate genome‐wide DNA demethylation and differentiate into oogonia/gonocyte‐like cells, demonstrating their germline potential. By creating a paradigm for hPGCLC expansion, our study uncovers critical divergences in expansion potential and the mechanism for epigenetic reprogramming between the human and mouse germ cell lineage.

中文翻译：

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人类原始生殖细胞样细胞在体外具有生殖潜能的长期扩增。

人类生殖细胞使人类遗传和表观遗传信息永存。然而，由于缺乏适当的实验系统，潜在的机制仍然难以捉摸。在这里，我们表明源自人类诱导多能干细胞 (hiPSCs) 的人类原始生殖细胞样细胞 (hPGCLCs) 可以在4 个月的时间内在体外确定的条件下繁殖至少 ~10 ⁶倍. 在扩增过程中，hPGCLCs 维持早期的 hPGC 样转录组并保留其全基因组 DNA 甲基化谱，这很可能是由于维持 DNA 甲基转移酶活性的保留。这些特征与小鼠 PGCLC 的特征形成鲜明对比，后者在类似条件下表现出有限的繁殖（高达约 50 倍）且仅持续约 1 周，但仍会经历细胞自主基因组范围的 DNA 去甲基化。重要的是，在异种重建卵巢中与小鼠胚胎卵巢体细胞聚集培养后，扩增的 hPGCLC 启动全基因组 DNA 去甲基化并分化为卵原细胞/生殖细胞样细胞，证明了它们的种系潜力。通过创建 hPGCLC 扩展的范例，