Mechanisms regulating competency of hepatocyte plasticity - PROJECT ABSTRACT Intrahepatic bile duct (IHBD) paucity is a major cause of pediatric liver disease, leading to significant morbidity and mortality. It results in chronic cholestasis, and often necessitates liver transplantation, which remains the only definitive treatment. IHBD paucity is associated with conditions such as Alagille syndrome (ALGS), progressive familial intrahepatic cholestasis (PFIC), and biliary atresia, yet no clinical interventions currently exist to augment IHBD architecture. Hepatocyte-to-cholangiocyte reprogramming—a process whereby hepatocytes acquire cholangiocyte characteristics—has emerged as a potential therapeutic approach. Genetic models of IHBD paucity demonstrate the ability of hepatocytes to reprogram under cholestatic stress, forming functional IHBD networks that effectively drain bile and persist after injury reversal. Importantly, reprogramming appears to require a stereotyped selective engagement of chromatin remodeling and transcriptional activation as well as repression programs, enhancing the completion of the hepatocyte conversion. Key barriers remain, such as fully repressing the original hepatocyte program to prevent hybrid cell states or deleterious outcomes, like cancer. Unique human-mouse integrated datasets, including liver samples from infancy through adulthood, provide new insights into temporal competence for reprogramming, showing that factors like age, spatial zonation, and gene regulation influence outcomes. Interestingly we have found that hepatocyte age impacts their chromatin accessibility at cholangiocyte-specific loci. The research explores two specific aims: 1) testing how Notch threshold levels and temporal factors dictate zonation-specific reprogramming sensitivity, and 2) defining Prdm16’s role, as a histone methyltransferase, in regulating chromatin and facilitating hepatocyte-to-cholangiocyte reprogramming. By combining cutting-edge techniques, including refined lineage-tracing mouse models, paired RNA expression and chromatin accessibility data, and human liver datasets, the study seeks to overcome translational barriers. This research promises to expand our understanding and the molecular underpinnings of reprogramming to optimize future cell/gene therapies with the promise to improve therapies for IHBD-related diseases like ALGS.
