Generation of rat liver organoid lines and their engraftment in a rat model of liver failure. Rat liver stem cells

The rat is an important model for pharmacological research, with the liver as the most important organ as metabolism studies and toxicity assays are frequently performed on primary rat hepatocytes. An in vitro culture system that captures the massive proliferation that can be observed after partial hepatectomy could serve as a consistent reliable source for these pharmacological studies and may cut down on the use of animal testing. As a first step towards this goal, we here describe the generation of rat liver stem cell lines from the BN-Lx and SHR strains, the two founder strains of the rat HXB/BXH recombinant inbred panel. Rat liver stem cells, which grow as cystic organoids, were characterized by high expression of the stem cell marker Lgr5, by the expression of liver progenitor and duct markers, and by low expression of hepatocyte markers, oval cell markers, and stellate cell markers. Prolonged cultures of rat liver organoids depended on high levels of WNT and the inhibition of BMP-signaling. Upon transplantation of clonal lines to a Fah-/- Il2rg-/- rat model of liver failure, the rat liver stem cells engrafted into the host liver where they differentiated into areas with FAH and Albumin positive hepatocytes. Conclusion: Rat liver stem cell lines thus hold potential for pharmacological, toxicological or metabolic studies and presents an alternative to the frequently used primary rat hepatocytes. To our knowledge, the here described liver stem cell lines represent the first organoid culture system in the rat.