Extracellular matrix flow guides in-vitro epithelial morphogenesis

Changes in spatial localization of the extracellular matrix (ECM) are necessary for establishing morphogenesis in multiple developmental contexts. Both ECM motion and tissue deformation require multicellular scale coordination, however the interplay between them remain largely unexplored. Here, we reveal a novel mechanism coupling morphogenetic events and epithelia-driven ECM flow in vitro. We show that exposure to ECM components triggers periodic morphogenesis of dome-shaped structures in human pluripotent stem cell (hPSC) monolayers, driven by directional ECM flow. We show that this flow is initiated by local symmetry breaking events, is driven by microvilli and requires unperturbed flow conditions, microvilli function, and cytoskeletal contractility. An in silico model shows that a reaction-diffusion-like mechanism is responsible for organizing local morphogenesis into global tissue-wide events. We validate this model by predicting changes in cell patterning landscape during mesoderm differentiation, and demonstrate changes in cellular identity by immunohistochemistry and scRNAseq. These results demonstrate that transport of ECM over epithelia, termed ECM flow, is a major contributor in sustaining morphogenesis and differentiation. Our in vitro approach suggests that ECM flow may be a broadly conserved mechanism guiding multi-cellular morphogenesis and may be further explored to investigate the role of ECM transport in other model systems.