Rebuilding the liver with adult hepatic and embryonic stem cells

An efficient system for differentiation, expansion and isolation of hepatic progenitor cells from mouse embryonic stem (ES) cells in vitro has been established. Using mouse ES cells transfected with green fluorescent protein (GFP) reporter gene regulated by albumin (ALB) enhancer/promoter, we show that serum-free, chemically defined medium supports formation of embryoid bodies (EBs) and differentiation of hepatic lineage cells in the absence of exogenous growth factors or feeder cell layers. The GFP+ cells acquired hepatocyte-like morphology and hepatocyte-specific markers (i.e. ALB, AAT, TO and G6P) and by 28 days represented more than 30% of cells isolated from EB outgrowths. The GFP+ cells developed into functional hepatocytes without cell fusion and participated in repairing of diseased liver when transplanted into MUP-uPA/SCID mice. In conclusion, a highly enriched population of committed hepatocyte precursors can be generated from ES cells in vitro for effective cell replacement therapy.