Large-Scale Bioprinting of Human Epiblast-Like Models Featuring Disc-Shaped Morphogenesis and Gastrulation Events.

Understanding the initial weeks of human development remains challenging due to ethical concerns and the restricted availability of human embryos. Pluripotent stem cell (PSC)-derived epiblast models mimicking gastrulation processes have sparked significant interest in bridging this gap. However, as a newly emerging field, bioengineered models show limited production throughput and complexity in recapitulating epiblasts' disc-shaped morphogenesis. Here, a well-defined laminin/alginate bioink to create epiblast-like models from human induced pluripotent stem cells (hiPSCs) using electro-assisted bioprinting is proposed. This approach enables the generation of large-scale hiPSC-laden microgels that not only facilitate mass transfer but also mimic the structural characteristics of early embryos, which allow hiPSCs to self-organize into disc-like epiblast models with consistent morphology and phenotype. With adaptability to human embryonic stem cells, this method demonstrates the versatility of engineering reproducible epiblast-like models using various PSC lineages. Importantly, the bioactive components and physical confinement provided by the bioink, and the endogenous regulation of the WNT signaling pathway, contribute to disc-like morphogenesis, recapitulation of epithelial-to-mesenchymal transition critical in the gastrulation process, and generation of the posterior epiblast population, directing the mass production of manipulable embryonic models for studying the spatiotemporal events and possible defects in early human development.