Intrinsic factors and the embryonic environment influence the formation of extragonadal teratomas during gestation.
Intrinsic factors and the embryonic environment influence the formation of extragonadal teratomas during gestation.
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DOI：
10.1186/s12861-015-0084-7
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发表时间：
2015-10-09
影响因子：
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通讯作者：
Wilson V
中科院分区：
文献类型：
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作者：
Economou C;Tsakiridis A;Wymeersch FJ;Gordon-Keylock S;Dewhurst RE;Fisher D;Medvinsky A;Smith AJ;Wilson V
多能细胞存在于早期胚胎中，直到体节发生开始时多能性调节因子 Oct4 的水平下降。在体外提高外植后多能细胞中的 Oct4 水平可恢复其多能性。当将培养的多能细胞引入宿主胚胎直至原肠胚形成结束时，可以参与正常发育。相比之下，多能细胞有效地在成年动物中播下恶性畸胎癌的种子。在人类中，性腺外畸胎瘤和畸胎癌最常见于新生儿的骶尾部区域，这表明这些肿瘤起源于胚胎后部的细胞，这些细胞要么重新激活，要么无法关闭其多能状态。然而，缺乏胚胎发育过程中多能性持续或重新激活的实验模型。 我们将胚胎干细胞手动注射到 E9.5 的受孕体内，以测试该阶段多能细胞的存在是否与畸胎瘤形成相关。然后，我们分别使用携带 PS/TB 特异性异源基因表达盒的转基因小鼠系和胚胎嵌合体，检查了在原条 (PS)/尾芽 (TB) 内普遍或与 Nanog 组合重新激活胚胎 Oct4 表达的效果。在这里，我们证明多能细胞在原肠胚形成后的胚胎中播种畸胎瘤。然而，在这些阶段，诱导的 Oct4 普遍表达并不会导致多能性的恢复（由 Nanog 表达表示）和子宫内肿瘤形成，而是导致前后轴延伸的严重表型。使用更受限制的 T(Bra) 启动子转基因系统，能够诱导 Oct4 和 Nanog 的异位表达，特别是在位于后部的原条 (PS) 和尾芽 (TB) 中，导致与单独使用 Oct4 诱导的类似的轴向畸形。这些细胞在来自体细胞发生阶段胚胎的外胚层干细胞（EpiSC）外植体中诱导多能性标记表达，但在体内未观察到畸胎瘤形成。我们的研究结果表明，尽管通过在外植的体细胞发生阶段体细胞中过度表达多能性调节因子可以在体外产生具有致畸潜能的多能细胞，但这些基因的体内诱导不会产生肿瘤。这表明胚胎微环境在多能性诱导中具有限制性调节作用。本文的在线版本 (doi:10.1186/s12861-015-0084-7) 包含补充材料，可供授权用户使用。
Pluripotent cells are present in early embryos until the levels of the pluripotency regulator Oct4 drop at the beginning of somitogenesis. Elevating Oct4 levels in explanted post-pluripotent cells in vitro restores their pluripotency. Cultured pluripotent cells can participate in normal development when introduced into host embryos up to the end of gastrulation. In contrast, pluripotent cells efficiently seed malignant teratocarcinomas in adult animals. In humans, extragonadal teratomas and teratocarcinomas are most frequently found in the sacrococcygeal region of neonates, suggesting that these tumours originate from cells in the posterior of the embryo that either reactivate or fail to switch off their pluripotent status. However, experimental models for the persistence or reactivation of pluripotency during embryonic development are lacking. We manually injected embryonic stem cells into conceptuses at E9.5 to test whether the presence of pluripotent cells at this stage correlates with teratocarcinoma formation. We then examined the effects of reactivating embryonic Oct4 expression ubiquitously or in combination with Nanog within the primitive streak (PS)/tail bud (TB) using a transgenic mouse line and embryo chimeras carrying a PS/TB-specific heterologous gene expression cassette respectively. Here, we show that pluripotent cells seed teratomas in post-gastrulation embryos. However, at these stages, induced ubiquitous expression of Oct4 does not lead to restoration of pluripotency (indicated by Nanog expression) and tumour formation in utero, but instead causes a severe phenotype in the extending anteroposterior axis. Use of a more restricted T(Bra) promoter transgenic system enabling inducible ectopic expression of Oct4 and Nanog specifically in the posteriorly-located primitive streak (PS) and tail bud (TB) led to similar axial malformations to those induced by Oct4 alone. These cells underwent induction of pluripotency marker expression in Epiblast Stem Cell (EpiSC) explants derived from somitogenesis-stage embryos, but no teratocarcinoma formation was observed in vivo. Our findings show that although pluripotent cells with teratocarcinogenic potential can be produced in vitro by the overexpression of pluripotency regulators in explanted somitogenesis-stage somatic cells, the in vivo induction of these genes does not yield tumours. This suggests a restrictive regulatory role of the embryonic microenvironment in the induction of pluripotency. The online version of this article (doi:10.1186/s12861-015-0084-7) contains supplementary material, which is available to authorized users.