Optimal Hypoxia Regulates Human iPSC-Derived Liver Bud Differentiation through Intercellular TGFB Signaling

Timely controlled oxygen (O2) delivery is crucial for the developing liver. However, the influence of O2 on intercellular communication during hepatogenesis is unclear. Using a human induced pluripotent stem cell-derived liver bud (hiPSC-LB) model, we found hypoxia induced with an O2-permeable plate promoted hepatic differentiation accompanied by TGFB1 and TGFB3 suppression. Conversely, extensive hypoxia generated with an O2-non-permeable plate elevated TGFBs and cholangiocyte marker expression. Single-cell RNA sequencing revealed that TGFB1 and TGFB3 are primarily expressed in the human liver mesenchyme and endothelium similar to in the hiPSC-LBs. Stromal cell-specific RNA interferences indicated the importance of TGFB signaling for hepatocytic differentiation in hiPSC-LB. Consistently, during mouse liver development, the Hif1a-mediated developmental hypoxic response is positively correlated with TGFB1 expression. These data provide insights into the mechanism that hypoxia-stimulated signals in mesenchyme and endothelium, likely through TGFB1, promote hepatoblast differentiation prior to fetal circulation establishment. •Mesenchyme (MC) and endothelium (EC) in human liver buds primarily express TGFBs•Hypoxia modulates TGFBR ligand expressions•TGFB suppression in EC and MC promotes hepatoblast differentiation•Optimal hypoxia-stimulated TGFB signal promotes hepatoblast differentiation To delineate the influence of O2 on liver development, human induced pluripotent stem cell-derived liver buds were used as a fetal liver model. This model provides insight into hypoxic modulation of mesenchyme-derived TGFB signals that promote hepatoblast differentiation in developing liver buds prior to blood circulation.