Development of intrahepatic bile ducts in rat foetal liver explants in vitro.

The origin of intrahepatic bile ducts was investigated in organ cultures of 13, 16 and 19-day foetal rat livers embedded for up to 10 days in a semi-solid agar gel on a filter-raft assembly. Following 10 days in culture, 13-day foetal explants consisted of liver cell trabeculae lined by endothelial cells. Although maturation of the liver cells and bile canaliculi was observed, duct development was found in less than 10% of the explants. Supplementation of the media with putative inducers of bile duct development or culture of explants adjacent to other tissues did not induce regular duct development. By contrast, explants from the porta hepatis of 19-day foetuses cultured for 4 days, but not 10 days, regularly contained duct-like structures. The formation of the few ducts in cultures of 13-day foetal liver explants indicates that these cells can arise by transformation of hepatoblasts but that specific inducers of development are required for predictable and continuous differentiation of biliary epithelial cells.