Single cell analysis of human fetal liver captures the transcriptional profile of hepatobiliary hybrid progenitors

The liver parenchyma is composed of hepatocytes and bile duct epithelial cells (BECs). Controversy exists regarding the cellular origin of human liver parenchymal tissue generation during embryonic development, homeostasis or repair. Here we report the existence of a hepatobiliary hybrid progenitor (HHyP) population in human fetal liver using single-cell RNA sequencing. HHyPs are anatomically restricted to the ductal plate of fetal liver and maintain a unique transcriptional profile distinct from fetal hepatocytes, mature hepatocytes and mature BECs. In addition, molecular heterogenicity within the EpCAM+ population of freshly isolated fetal and adult human liver reveals diverse gene expression signatures of hepatic and biliary lineage potential. Finally, we FACS isolated fetal HHyPs and confirmed their hybrid progenitor phenotype in vivo. Our study suggests that hepatobiliary progenitor cells previously identified in mice also exist in humans, and can be distinguished from other parenchymal populations, including mature BECs, by distinct gene expression profiles.