Investigation of embryogenesis in a dish: the development and application of gastruloid models from pluripotent stem cells

Gastrulation constitutes a critical phase of mammalian embryogenesis, during which the embryo undergoes morphological changes, germ layer determination, and body axes establishment, laying the foundation for subsequent embryonic development. However, due to the technical and ethical restrictions, embryo-based studies during the gastrulation period are limited in both the scope of scientific questions worth exploring and experimental tractability. Gastruloids, three-dimensional aggregates recapitulating embryos at the gastrulation stage, emerge as an in vitro platform to dissect the dynamics of this process. Owing to their high-throughput and tractable advantages, gastruloids hold broad application potential. In this review, we summarize current knowledge on mammalian embryogenesis and the insights from both mouse and human gastruloid models. We also discuss the current applications of gastruloids in embryogenesis, disease modeling, drug development, and regenerative medicine.