Definitive Endoderm from EpiSC Aggregates in Matrigel.

This chapter describes the protocol to derive definitive endoderm cells from epiblast stem cells (EpiSCs) via a process analogous to gastrulation in embryos. The basis of this protocol mimicking the in vivo gastrulation process makes a contrast with those using sequential administration of pharmacological molecules and recombinant signaling proteins even at nonphysiological levels. In the experimental setup, EpiSCs are first freed from the dish-adherent condition to form free-floating aggregates, where endoderm precursor pools are produced. Embedding the EpiSC aggregates in the Matrigel allows the endoderm precursors to interact with the Matrigel mimicking the laminin-rich basement membrane underlying the egg cylinder epiblast in embryos, and let the precursors migrate into the Matrigel-filled external zone and develop into endodermal epithelial tissues.