An in vitro model of the interaction between the extra-embryonic lineages of the peri-implantation human embryo

主题：健康的生物科学控制着床期灵长类胚胎形态发生的信号通路尚不完全清楚。在小鼠胚胎中，被称为前内脏内胚层（AVE）的信号传导中心分泌许多Nodal和Wnt拮抗剂（例如Lefty， Dkk1, Cer1），导致在胚胎AP轴上形成Nodal和Wnt活性梯度。有趣的是，在食蟹猴的下胚层中发现了av样细胞。这些av样细胞分泌WNT和BMP拮抗剂，而细胞滋养细胞和羊膜细胞分别分泌WNT3A和BMP4。这表明灵长类胚胎的两种胚胎外谱系可能在外胚层上产生WNT和BMP梯度，这可能反过来协调羊膜形成甚至原肠胚形成。考虑到与人类胚胎植入后培养相关的技术和伦理障碍，该项目寻求利用具有代表性的干细胞系来模拟人类胚胎外和胚胎谱系在体外的相互作用。通过激活素A、WNT和LIF对人类多能干细胞（hPSCs）的处理，我们试图从代表着床前多能状态的hPSCs中获得一种人类低成母细胞样干细胞系：“naïve”多能状态。这是因为植入前ICM指定了下母细胞。为此，我们使用了“Rset”细胞系和人类扩展潜能多能干细胞（hEPSC）细胞系。我们还试图确定是否可以从传统的人类胚胎干细胞（hESC）中衍生出类似于植入后外胚层的“诱导”多能状态，从而确定不同的多能状态对hPSC向低成细胞规范的易感性的影响。我们还试图模拟这些acl处理的hPSCs和hESCs之间的相互作用，试图模拟外胚层-下胚层串扰，发现acl处理的hESCs通过抑制WNT和BMP信号传导来阻止hESC分化。

Theme: Bioscience for HealthThe signalling pathways that govern peri-implantation morphogenesis in the primate embryo are not fully understood. In the mouse embryo, a signalling centre known as the Anterior Visceral endoderm (AVE) secretes a number of Nodal and Wnt antagonists (e.g Lefty, Dkk1, Cer1), leading to the formation of a gradient of Nodal and Wnt activity across the AP axis of the embryo. Interestingly, AVE-like cells have been identified in the cynomolgus monkey hypoblast. These AVE-like cells secrete WNT and BMP antagonists, whereas cytotrophoblast and amniotic cells secrete WNT3A and BMP4, respectively. This suggests that the two extraembryonic lineages of the primate embryo may act to create a gradient of WNT and BMP gradient across the epiblast, which may in turn orchestrate amnion formation and also even gastrulation. Given the technical and ethical hurdles associated with the culture of human embryos post-implantation, this project seeks to model the interaction between the human extraembryonic and the embryonic lineages in vitro using stem cell lines representative of each. Via Activin A, WNT and LIF treatment of human pluripotent stem cells (hPSCs), we sought to derive a human hypoblast-like stem cell line from hPSCs representative of a pre-implantation pluripotent state: a "naïve" pluripotent state. This is because the hypoblast is specified from the pre-implantation ICM. For this, both the "Rset" cell line and the human extended potential pluripotent stem cell (hEPSC) line were used. We also sought to determine whether a hypoblast-like cell could be derive from the conventional human embryonic stem cell (hESC), which have a "primed" pluripotent state more similar to the post-implantation epiblast, and thus ascertain the influence that different pluripotent states has on amenability of a hPSC towards hypoblast-specification. We also seek to model the interaction between these ACL-treated hPSCs and hESCs in an attempt to model epiblast-hypoblast crosstalk, finding that ACL-treated hESCs act to prevent hESC differentiation via both WNT and BMP signalling inhibition.