Table 1.

A Summary of Different Stem Cell-Based Embryo Models to Study Early Embryonic Development

Type	PSC Source	Key Features/Cell Types	References
PASE	Human ESC	1.Resembles early post-implantation human embryonic development. 2.Luminogenesis of the epiblast, pro-amniotic activity, formation of embryonic sac, and primordial germ cell specification.	Shao et al., 2017a, 2017b; Zheng et al., 2019
Blastoid	Mouse ESCs and TSC, or mouse extended pluripotent stem cells alone	1.Morphologically and transcriptionally resemble E3.5 blastocysts. 2.Self-organization of mouse stem cells to form blastocyst-like structure containing epiblast (Epi), trophoectoderm (TE), and primitive endoderm (PE). 3.Triggers decidualization upon in utero transfer and forms tissues that progress along developmental trajectories but with limited organization overtime (similar to all embryo models that are currently available). Live fetus or mice were not generated.	Li et al., 2019b; Rivron et al., 2018b; Sozen et al., 2019
ETX model	Mouse ESC + TSC + XEN	1.Consist of ESC-derived epiblast, TSC-derived extra-embryonic ectoderm, and XEN-derived visceral endoderm. 2.Specifies mesoderm and definitive endoderm-like cells. 3.Resembles E7 mid-gastrula-stage embryo	Sozen et al., 2018
Gastruloid	Mouse ESC	1.Trunk-like structures with mediolateral axis and left-right asymmetry, presence of somites with correct rostrocaudal patterning. 2.Mimic embryonic spatial and temporal gene expression. 3.Generate neural tube, mesodermal and endodermal derivatives, and presence of segmentation clock.	Beccari et al., 2018; van den Brink et al., 2020; Veenvliet et al., 2020
	Human ESC	1.Form derivatives of three germ layers and undergo elongation along an anteroposterior axis. 2.Signature of somitogenesis resembling Carnegie-stage-9 embryos. Lack anterior neural structures.	Moris et al., 2020

PASE, Post-implantation Amniotic Sac Embryoid ; XEN, extra endodermal cell; TSC, Trophoblast stem cells.