Abstract
Understanding the unique mechanisms of human oogenesis necessitates the development of an in vitro system of stem cell differentiation into oocytes. Specialized cell types and organoids have been derived from human pluripotent stem cells in vitro, but generating a human ovarian follicle remains a challenge. Here we report that human embryonic stem cells can be induced to differentiate into ovarian follicle-like cells (FLCs) in vitro. First, we find that two RNA-binding proteins specifically expressed in germ cells, DAZL and BOULE, regulate the exit from pluripotency and entry into meiosis. By expressing DAZL and BOULE with recombinant human GDF9 and BMP15, these meiotic germ cells are further induced to form ovarian FLCs, including oocytes and granulosa cells. This robust in vitro differentiation system will allow the study of the unique molecular mechanisms underlying human pluripotent stem cell differentiation into late primordial germ cells, meiotic germ cells and ovarian follicles.
Highlights
Understanding the unique mechanisms of human oogenesis necessitates the development of an in vitro system of stem cell differentiation into oocytes
To determine whether the increase in DAZL can down regulate the expression of pluripotency markers in vitro, we modulated the level of DAZL expression in Human embryonic stem cells (hESCs) during differentiation with bone morphogenetic proteins (BMPs) BMP4 and BMP8a (Fig. 1c)
We found that 1 h of treatment with the BMPs induced the phosphorylation of pSmad1/5/8, indicating the differentiation of hESCs (Supplementary Fig. 1)
Summary
Understanding the unique mechanisms of human oogenesis necessitates the development of an in vitro system of stem cell differentiation into oocytes. The first successful derivation reported was the spontaneous differentiation of mouse ESCs using medium containing fetal bovine serum (FBS)[9], and the most recent method reported for obtaining oocyte-like cells in mice required the aggregation of primordial germ cells (PGCs) and somatic cells from E12.5 fetal gonads. This approach generated many oocyte-like cells, but the requirement of fetal ovarian tissues to obtain oocyte-like cells makes human studies technically challenging and may raise ethical issues. Transcriptome analysis, immunostaining of ovarian follicle markers and transplantation experiment all indicates that the follicle-like cells (FLCs) we derived resembling in vivo primordial follicle
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