Computational modelling unveils how epiblast remodelling and positioning rely on trophectoderm morphogenesis during mouse implantation

Abstract

<jats:title>Abstract</jats:title><jats:p>Understanding the processes by which the mammalian embryo implants in the maternal uterus is a long-standing challenge in embryology. New insights into this morphogenetic event could be of great importance in helping, for example, to reduce human infertility. During implantation the blastocyst, composed of epiblast and trophectoderm, undergoes significant remodelling from an oval ball to an egg cylinder. A main feature of this transformation is symmetry breaking and reshaping of the epiblast into a “cup”. Based on previous studies, we hypothesise that this event is the result of mechanical constraints originating from the trophectoderm, which is also significantly transformed during this process. In order to investigate this hypothesis we propose MG#, an original computational model of biomechanics able to reproduce key cell shape changes and tissue level behaviours <jats:italic>in silico</jats:italic>. With this model, we simulate epiblast and trophectoderm morphogenesis during implantation. First, our results uphold experimental findings that repulsion at the apical surface of the epiblast is sufficient to drive lumenogenesis. Then, we provide new theoretical evidence that trophectoderm morphogenesis indeed dictates the cup shape of the epiblast and fosters its movement towards the uterine tissue. Together, these results offer mechanical insights into mouse implantation and highlight the usefulness of agent-based modelling methods in the study of embryogenesis.</jats:p><jats:sec><jats:title>Author summary</jats:title><jats:p>Computational modelling is increasingly used in the context of biological development. Here we propose a novel agent-based model of biological cell and tissue mechanics to investigate important morphological changes during mouse embryo implantation. Our model is able to replicate key biological cell shape changes and tissue-level behaviour. Simulating mouse implantation with this model, we bring theoretical support to previous experimental observations that lumenogenesis in the epiblast is driven by repulsion, and provide theoretical evidence that changes in epiblast shape during implantation are regulated by trophectoderm development.</jats:p></jats:sec>

Epithelial-Mesenchymal Transition Drives Three-Dimensional Morphogenesis in Mammalian Early Development

“…Non-polarized naïve epiblast precursors at this stage do not respond to mechanical stimuli (Verstreken et al, 2019 ). Later on, at the peri-implantation stage, upon ECM-mediated epiblast epithelialization, the luminal pressure will induce apical surface repulsion, which contributes to the fusion of multiple rosette-like clusters and to the establishment of inverted cup shaped-morphology of the mouse embryo (Christodoulou et al, 2018 ; Dokmegang et al, 2020 ). In parallel, the progression of epiblast cells from non-polarized naïve pluripotent cells to apicobasally polarized primed cells enables biomechanical signaling to play a role in epiblast cells' fate decisions (Verstreken et al, 2019 ).…”