Embryoids, organoids and gastruloids: new approaches to understanding embryogenesis

Abstract

Cells have an intrinsic ability to self-assemble and self-organize into complex and functional tissues and organs. By taking advantage of this ability, embryoids, organoids and gastruloids have recently been generated in vitro, providing a unique opportunity to explore complex embryological events in a detailed and highly quantitative manner. Here, we examine how such approaches are being used to answer fundamental questions in embryology, such as how cells selforganize and assemble, how the embryo breaks symmetry, and what controls timing and size in development. We also highlight how further improvements to these exciting technologies, based on the development of quantitative platforms to precisely follow and measure subcellular and molecular events, are paving the way for a more complete understanding of the complex events that help build the human embryo.

Cell signalling stabilizes morphogenesis against noise

“…Our results are also consistent with the large, and mostly random, morphological variability of embryoids (Simunovic & Brivanlou, 2017). In those we observe how the simple activation of cell behaviors can lead to relatively complex morphologies.…”

“…In those we observe how the simple activation of cell behaviors can lead to relatively complex morphologies. Embryoids lack the spatially confined patterns of gene expression observed in vivo and that in our study are required for developmental stability (Simunovic & Brivanlou, 2017). This, together with the inevitably more noisy in vitro environment, may explain the large developmental instability of embryoids' morphology.…”

Human fetal adrenal cells retain age‐related stem‐ and endocrine‐differentiation potential in culture

“…The coexistence in in vitro culture of these different cell types, capable of maintaining their ontogenetic program, enables the formation of a specific organoid, defined as an in vitro 3D-cellular cluster derived from primary tissue, characterized by self-renewal and self-organization and exhibiting similar organ functionality as the tissue of origin (37)(38)(39). Herein, we provide evidence of the ability of the primary mixed fetal adrenal cell populations to spontaneously generate in vitro 3D structures resembling the original fetal organ.…”

Ethical issues in human organoid and gastruloid research

“…Another phenomenon observed under certain in vitro conditions is the self-organization of mouse and human PSCs into structures that recapitulate key developmental features of gastrulation (van den Brink et al, 2014;Warmflash et al, 2014, reviewed in this issue by Simunovic and Brivanlou, 2017). Referred to as 'gastruloids', these complex structures are distinct from organoids in that they do not recapitulate an organ per se, but rather a developmental process.…”