Reconstructing human early embryogenesis in vitro with pluripotent stem cells

Abstract

Understanding human development is of fundamental biological and clinical importance. Yet despite its significance, insights into early developmental events in humans still remain largely unknown. While recent advances show that stem cells can mimic embryogenesis1-9 to unravel hidden developmental mechanisms, a stem cell- based model of early human embryogenesis is lacking. Here, we use human extended pluripotent stem cells10 to reconstitute early human development in 3-dimensions and recapitulate early embryo-like events. We first perform a systematic characterisation to reveal unique signalling requirements for building the human pre-implantation blastocyst. Further, we show that these in vitro stem cell-derived blastocyst-like structures are able to undertake spatiotemporal self-organisation to mimic peri- implantation remodelling in which a polarised rosette opens up the amniotic cavity within a developing disc. The hallmarks of human early development displayed by this stem cell-based in vitro model mimics features of embryonic day 3 to day 9/10 of natural development. Thus, this platform represents a tractable model system to contribute to the basic understanding of cellular and molecular mechanisms governing early embryonic events in humans and to provide valuable insights into the design of differentiation protocols for human stem cells in clinical applications.

Hypoxia induces a transcriptional early primitive streak signature in pluripotent cells enhancing spontaneous elongation and lineage representation in gastruloids

“…Overall, our gastruloid data point to the importance of using physiologically relevant oxygen concentrations in models of embryo development. This is further corroborated by recent studies demonstrating that hypoxic culture conditions increase both the efficiency of the formation of blastocyst-like structures from human and mouse pluripotent stem cells, and ex utero culture of embryos from postimplantation to early organogenesis stages (Aguilera-Castrejon et al, 2021;Sozen et al, 2019Sozen et al, , 2021. Thus, in addition to other modulators of the microenvironment such as medium composition, and matrix, we suggest oxygen tension to be taken into consideration when modelling developmental processes in a dish, or culturing mammalian embryos ex utero.…”

Human embryonic development: from peri-implantation to gastrulation

“…Human blastoids are reassembled by aggregating a mixed population of incompletely defined stem cells (with epiblast, trophectoderm, or hypoblast-like signatures) reprogrammed from human fibroblast cells, which not only display morphologically comparable features as blastulas but also can attach to the tissue culture plates and develop into E10-like embryos with the lumenogenesis of proamniotic sac-like structure [28] (Box 1). Naïve pluripotent stem cells or hEPSCs can be also used in the construction of blastoids because of their potent differentiation capacity [29][30][31][32] (Box 4). Even though both blastoids stop their development at the E10-like stage, the significant events during this stage, especially the implantation, could be sufficiently elucidated.…”

“…Mouse integrated blastoids have been constructed by the aggregation of mouse expanded potential stem cells, and they can induce decidualization of the endometrium and further implant into the uterus, although they exhibit limited developmental capacity and disorganize structures at the putative gastrulation stage [36]. A similar method has been applied recently to establish human blastoids by hESPCs, iPSCs, or naïve ESCs, which are morphologically and transcriptomically akin to natural blastulas and can develop into an E10-like stage [29,31,32] (Box 1).…”

Studying evolution of the primary body axis in vivo and in vitro

“…A series of very recent studies with hPSCs (induced or otherwise) demonstrated that also human blastocyst-like structures (hBlastoids) can be successfully obtained by either mixing hESCs with SCs from extra-embryonic lineages or via employing naïve hEPSCs, akin to the mouse model ( Liu et al, 2021 ; Yu et al, 2021 ; Sozen et al, 2021 ; Fan et al, 2021 ).…”