Chemically defined and growth factor-free system for highly efficient endoderm induction of human pluripotent stem cells [ATAC-seq]
Definitive endoderm (DE) derived from human pluripotent stem cells (hPSCs) holds great promise for cell-based therapies and drug discovery. However, current DE differentiation methods required undefined components and/or expensive recombinant proteins, limiting their scalable manufacture and clinical use. Homogeneous DE differentiation in defined and recombinant protein-free conditions remains a major challenge. Here, by systematic optimization and high-throughput screening, we report a fully synthetic, small molecule-based defined system that contains only four components (4C), enabling highly efficient and cost-effective DE specification of hPSCs in the absence of recombinant proteins. 4C-induced DE can differentiate into functional hepatocytes, lung epithelium, and pancreatic ß cells in vitro and multiple DE-derivatives in vivo. Genomic accessibility analysis reveal that 4C reconfigures chromatin architecture to allow key DE transcription-factor binding and identify TEAD3 as a novel key DE regulator. This system may facilitate mass production of mature DE-derivatives for drug discovery, disease modelling, and cell therapy. Overall design: Bulk ATAC-seq  was performed on human embryonic stem cells (hESCs) at various time points (Day 0, 1, 2, and 3) following their treatment with Vitamin C (Vc) or LDN.