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 foetal liver using single-cell RNA sequencing. HHyPs are anatomically restricted to the ductal plate of foetal liver and maintain a transcriptional profile distinct from foetal hepatocytes, mature hepatocytes and mature BECs. In addition, molecular heterogeneity within the EpCAM + population of freshly isolated foetal and adult human liver identifies diverse gene expression signatures of hepatic and biliary lineage potential. Finally, we FACS isolate foetal HHyPs and confirm 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.

Recent advancements in the production of hepatocytes from human pluripotent stem cells (hPSC‐Heps) afford tremendous possibilities for treatment of patients with liver disease. Validated current good manufacturing practice (cGMP) lines are an essential prerequisite for such applications but have only recently been established. Whether such cGMP lines are capable of hepatic differentiation is not known. To address this knowledge gap, we examined the proficiency of three recently derived cGMP lines (two hiPSC and one hESC) to differentiate into hepatocytes and their suitability for therapy. hPSC‐Heps generated using a chemically defined four‐step hepatic differentiation protocol uniformly demonstrated highly reproducible phenotypes and functionality. Seeding into a 3D poly(ethylene glycol)‐diacrylate fabricated inverted colloid crystal scaffold converted these immature progenitors into more advanced hepatic tissue structures. Hepatic constructs could also be successfully encapsulated into the immune‐privileged material alginate and remained viable as well as functional upon transplantation into immune competent mice. This is the first report we are aware of demonstrating cGMP‐compliant hPSCs can generate cells with advanced hepatic function potentially suitable for future therapeutic applications. stem cells translational medicine 2019;8:124&14

The liver is largely composed of hepatocytes and bile duct epithelial cells (BECs). Controversy exists as to whether a liver stem/progenitor cell capable of renewing both hepatocytes and BECs exists. Single cell RNA sequencing of freshly isolated human foetal and healthy adult liver identified hepatocyte, hepatoblast and liver progenitor cell (hLPC) populations. hLPCs, found at the interface between hepatocytes and bile ducts in both foetal and adult tissue, were distinguishable from BECs by their negative expression of TROP-2. Prospective isolation followed by in vitro culture demonstrated their potential for expansion and bi-lineage differentiation. The hLPC expression signature was also conserved within expanded cell populations specific to certain cases of liver injury and cancer. These data support the idea of a true progenitor existing within healthy adult liver that can be activated upon injury. Further work to define the mechanisms regulating hLPC behaviour could advance understanding of human development and disease.2 All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.

Alpha-1 antitrypsin deficiency (A1ATD) is a life-threatening condition caused by inheritance of the SERPINA1-Z genetic variant (PiZ) leading to protein misfolding and liver toxicity. There remain no approved medicines for this disease. Here we report the results of a small molecule screen performed in patient-derived iPSC hepatocytes that identified Leucine-rich repeat kinase-2 (LRRK2), as a potentially new therapeutic target. Genetic deletion of LRRK2 in PiZ mice reduced both intrahepatic misfolded polymers and fibrosis leading us to test a library of commercially available LRRK2 inhibitors across several cell models. One of these molecules, CZC-25146, a candidate with favourable pharmacokinetic properties, reduced polymer load, increased normal AAT secretion and reduced inflammatory cytokines in both cells and the PiZ mouse. Mechanistically, this effect was achieved via inhibition of LRRK2 kinase activity and autophagy induction. These findings support the use of CZC-25146 (and potentially LRRK2 inhibitors more broadly) in hepatic proteinopathy disease research and as potential new therapies.