Adult hepatocytes direct liver organogenesis through non-parenchymal cell recruitment in the kidney. Mus musculus

Background & Aims: Since the first account of the myth of Prometheus, the amazing regenerative capacity of the liver has fascinated researchers due to its enormous medical potential. Liver regeneration is promoted by multiple types of liver cells, including hepatocytes and liver non-parenchymal cells (NPCs), through the complex intercellular signaling. However, the liver organogenetic mechanism, especially the role of adult hepatocytes at ectopic sites, remains unknown. In this study, we demonstrate that hepatocytes alone spurred liver organogenesis to form an organ-sized complex 3D liver that exhibited native liver architecture and functions in the kidneys of mice. Methods: Isolated hepatocytes were transplanted under the kidney capsule of monocrotaline (MCT) and partial hepatectomy (PHx)-treated mice. To determine the origin of NPCs in neo-livers, hepatocytes were transplanted into MCT/PHx-treated green fluorescent protein (GFP) transgenic mice or wild-type mice transplanted with bone marrow (BM) cells isolated from GFP mice. Results: Hepatocytes engrafted at the subrenal space of mice underwent continuous growth in response to a chronic hepatic injury in the native liver. More than 1.5 yrs later, whole organ-sized liver tissues having a greater mass than those of the injured native liver had formed. Most remarkably, we revealed that at least three types of NPCs with similar phenotypic features to the liver NPCs were recruited from the host tissues including BM. The neo-livers in the kidney exhibited liver-specific functions and architectures, including sinusoidal vascular systems, zonal heterogeneity, and emergence of bile duct cells. Furthermore, the neo-livers successfully rescued the mice with lethal liver injury. Conclusion: Our data clearly showed that adult hepatocytes play a leading role as organizer cells in liver organogenesis at ectopic sites via NPC recruitment. Overall design: Donor hepatocytes were isolated from FVB/N-human α1-antitrypsin (hA1AT) transgenic (Tg) mice (8−20 weeks old). Wild-type FVB/N mice (7−9 weeks old) were used to develop a chronic hepatic injury model; these mice served as the recipients for hepatocyte donation. The recipient mice received two doses of monocrotaline (MCT) (70 mg/kg) into the intraperitoneal space at intervals of 2 weeks. Two weeks after the last injection of MCT, 1 × 10(6) isolated hepatocytes from FVB/N-hA1AT Tg mice were transplanted under the kidney capsule of the FVB/N mice. The total RNA was isolated from the recipient injured liver and kidney tissues, ectopic neo-livers microdissected from the kidneys on days 250−300, and the livers of normal mice (20-week-old).