Steroidogenesis from cholesterol in placental trophoblasts is fundamentally involved in the establishment and maintenance of pregnancy. The transcription factor gene heart and neural crest derivatives expressed 1 (Hand1) promotes differentiation of mouse trophoblast giant cells. However, the role of HAND1 in human trophoblasts remains unknown. Here, we report that HAND1 inhibits human trophoblastic progesterone (P4) and estradiol (E2) from cholesterol through downregulation of the expression of steroidogenic enzymes, including aromatase, P450 cholesterol side-chain cleavage enzyme (P450scc), and 3β-hydroxysteroid dehydrogenase type 1 (3β-HSD1). Mechanically, although HAND1 inhibits transcription of aromatase by directly binding to aromatase gene promoter, it restrains transcription of P450scc by upregulation of the methylation status of P450scc gene promoter through its binding to ALKBH1, a demethylase. Unlike aromatase and P450scc, HAND1 decreases 3β-HSD1 mRNA levels by the reduction of its RNA stability through binding to and subsequent destabilizing protein HuR. Finally, HAND1 suppresses circulating P4 and E2 levels derived from JEG-3 xenograft and attenuates uterine response to P4 and E2. Thus, our results uncover a hitherto uncharacterized role of HAND1 in the regulation of cholesterol metabolism in human trophoblasts, which may help pinpoint the underlying mechanisms involved in supporting the development and physiological function of the human placenta.

胎盘滋养细胞中胆固醇的类固醇生成从根本上涉及妊娠的建立和维持。表达的转录因子基因心脏和神经嵴衍生物1（ Hand1）促进小鼠滋养层巨细胞的分化。然而，HAND1在人类滋养细胞中的作用仍然未知。在这里，我们报告 HAND1 通过下调类固醇生成酶（包括芳香酶、P450 胆固醇侧链裂解酶 (P450scc) 和 3β-羟基类固醇脱氢酶 1 型）的表达来抑制胆固醇中的人滋养层黄体酮 (P4) 和雌二醇 (E2) (3β-HSD1)。机械地，虽然 HAND1通过直接结合到芳香酶基因启动子，它通过与去甲基酶 ALKBH1 的结合上调P4 50scc基因启动子的甲基化状态来抑制P4 50scc 的转录。与芳香化酶和 P450scc 不同，HAND1 降低3β-HSD1 mRNA 水平，方法是通过结合并随后破坏蛋白质 HuR 来降低其 RNA 稳定性。最后，HAND1 抑制源自 JEG-3 异种移植物的循环 P4 和 E2 水平，并减弱子宫对 P4 和 E2 的反应。因此，我们的研究结果揭示了 HAND1 在调节人类滋养细胞中胆固醇代谢中的一种迄今为止未被表征的作用，这可能有助于查明参与支持人类胎盘发育和生理功能的潜在机制。