P35 Cellular plasticity in human chronic liver disease is driven by transdifferentiation and is regulated by the PI3K-AKT-mTOR insulin pathway

<h3></h3> Liver regeneration is driven by cellular proliferation in acute liver disease. In contrast, the human liver regenerative mechanisms in chronic liver disease have been less well understood. These processes may involve stem cells, progenitor cells or facultative epithelial cells. Chronic liver disease is projected as a major health threat and therefore deep knowledge of these mechanisms is paramount in enabling liver repair treatments. Here we study the above hypotheses, and we show a molecular pathway involved in the regenerative process. We performed single nuclei RNA sequencing of 47 liver biopsies from patients across the spectrum of metabolic dysfunction-associated fatty liver disease (MASLD) and state-of-the-art 3D imaging combined with computational analysis to identify cellular dynamic changes across the progression of MASLD. Finally, we validated our in vivo findings using liver organoid technology, from MASLD patients. Our analysis has shown remarkable biliary re-organisation and the acquisition of epithelial plasticity towards the end stage of liver disease, evident by the presence of biphenotypic cells sharing cholangiocyte and hepatocyte features. These cells lacked markers of stem cells or progenitor cells, pointing towards transdifferentiation between cholangiocytes and hepatocytes as their main source. In addition, the PI3K-AKT-mTOR was found to be involved in their generation process, and this was validated in liver organoids. In conclusion, this study is the first and largest study to include patients undergoing single nuclei RNA sequencing across the spectrum of MASLD. It is arguing against the presence of stem cells as a driver of liver regeneration in chronic liver disease, a notion embedded in hepatology for more than 50 years. In fact, it suggests that cholangiocyte and hepatocyte transdifferentiation is the main regenerative mechanism of the chronically injured human liver and this process may be insufficient to rescue the liver. Further studies would be required to correlate this process with liver repair and liver dysplasia.