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

Timely controlled oxygen (O-2) delivery is crucial for the developing liver. However, the influence of O-2 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 O-2 -permeable plate promoted hepatic differentiation accompanied by TGFB1 and TGFB3 suppression. Conversely, extensive hypoxia generated with an O-2-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 Hifla-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.